Few dinosaurs are as well studied as the Upper Cretaceous tyrannosaurid theropod Tyrannosaurus rex. It might be easy to assume that this intense focus has been driven by the fame and glory associated with working on this dinosaur. That might be partly true but, in fact, T. rex really is one of the best known dinosaurs, represented by multiple individuals that are often near-complete and well preserved. It has also - in the form of bite marks, coprolites and soft tissue traces (or alleged soft tissue traces) - left us more evidence of its behaviour than many other Mesozoic dinosaurs. T. rex might really be regarded, then, as a 'model dinosaur', and its familiarity and popularity might instead be argued to be coincidental, the result of its relatively early discovery (it was named in 1905) and of its status as one of the world's largest predatory dinosaur. In celebration of 100 years of knowledge of the world's most famous dinosaur, the Black Hills Institute of Geological Research (Hill City, South Dakota) held '100 Years of Tyrannosaurus rex: A Symposium' in June 2005. Including 21 contributions from 30 authors, this book is the result.
The volume starts with Neal Larson's review of all reported T. rex skeletons. This is an interesting catalogue, providing and illustrating a great deal of obscure and even never-before-published information. Here, we receive the first indication that not everyone involved in tyrant dinosaur research agrees on the taxonomy of the population of animals generally referred to as T. rex. Referring to the fact that 'there is so much evidence separating Nanotyrannus from T. rex' (p. 2), Larson retains Nanotyrannus as a distinct taxon (as do some other contributions in the volume). He also notes the even less well known opinion of Stephan Pickering that FMNH PR2081 (aka 'Sue', previously BHI 2033) and a few other specimens represent a distinct species, but Larson disagrees and so does everyone else I think. Unmentioned (and clearly little known) is that yet another alleged Tyrannosaurus species, T. vannus from Big Bend National Park, was named in an unpublished thesis filed by Douglas Lawson in 1972. Several workers have noted that this specimen (the holotype is the left maxilla TMM 41436-1) falls outside the range of variation of T. rex (most recently, Brochu (2003) said that, if it is not T. rex, it represents a close relative), but we are still waiting for a definitive reassessment.
When T. rex was first described by Henry Osborn in 1905, it was described alongside a second gigantic theropod, the armour-plated Dynamosaurus imperiosus [early reconstruction shown here]. Brent Breithaupt and colleagues provide a brief review of Dynamosaurus and other tyrant dinosaur discoveries from the Rocky Mountain West. It is well known that the Dynamosaurus type specimen - sold to the British Museum (Natural History) in 1960 - was mounted in the museum's old dinosaur gallery in a rather 'modern' pose: that is, with its body and tail near-horizontal and its tail well up off the ground. Those who have commented on this have usually noted that Barney Newman wanted to depict the animal in a dynamic, modern pose, and said as much in a technical paper (Newman 1970). I was therefore interested to read Alan Charig's comment that the specimen 'was mounted with its body in a far too horizontal position: this was done because it would otherwise have been too tall for the Gallery. Newman, who made the mount, has attempted to rationalise this (1970) by stating that the posture was much more bird-like than is suggested by earlier mounts' (Charig 1972, p. 137) [the mount in question is shown below; an article devoted to it previously appeared here].
Mary Schweitzer and colleagues review their recent discoveries on medullary bone in T. rex and Peter Larson looks at variation within the species. While T. rex seems to include both gracile and robust individuals, Larson also discusses the idea that Nanotyrannus - argued by Carr (1999) to represent a juvenile T. rex, contra Bakker et al. (1988) - is a distinct taxon. Less familiar is the idea that what is generally known as T. rex possibly includes two species, with the 'other one' known provisionally as Tyrannosaurus "x". To my knowledge, the only other outing of this idea in the literature is some very brief discussion in Horner and Lessem's popular book The Complete T. Rex where this notion is mentioned as one of Robert Bakker's pet hypotheses (indeed, Larson states here that the Tyrannosaurus "x" hypothesis originated with Bakker). While this is very much a minority opinion, the idea that there might have been more than one contemporaneous species in the genus is hardly crazy radical nonsense. Indeed, Maastrichtian western North America was highly unusual in apparently being home to but a single species of large theropod. Ultimately, I found the arguments put forward by Larson unconvincing however: the features suggested to distinguish the two overlap (like number of maxillary or dentary teeth), or are known to be variable in other taxa (like size of the pneumatic foramen in the lacrimal).
Proposing an 'integral morphodynamic solution' to tyrant dinosaur body shape and proportions, Martin Lockley and colleagues dismiss the idea that adaptation provides the explanation for the striking skull and forelimb proportions. They argue instead that 'morphodynamic compensation' explains how the diminutive forelimbs of these theropods were an accidental consequence of genetic investment in the proportionally gigantic skull. This is easily the strangest and most problematic contribution to the book, and even within the volume itself, other authors (Lipkin and Carpenter) note that these conclusions are untestable and speculative. Lockley and collegues have recently used similar arguments to explain the presence of short tails in pterodactyloid pterosaurs. Their arguments need to be properly evaluated by someone active in the field of evo-devo, but I find it hard to take them seriously. The dismissal of adaptation as an explanation for a given bauplan is strange given that this is one of the most fundamental concepts in evolutionary theory ['Sue', aka FMNH PR2081, shown below. From wikipedia].
Christine Lipkin and Kenneth Carpenter look anew at forelimb function in T. rex. In keeping with some previous work on the subject, the authors conclude, based on evidence from pathologies, reconstructed musculature and mathematical modelling, that the short arms of T. rex were very powerful and perhaps played a role in predation. In view of Brochu's (2003) critique they revisit the too-avian reconstruction previously published by Carpenter and Smith (2001). However, given that these dinosaurs had banana-shaped teeth over 15 cm long and could literally bite animals in half with an astronomically high bite-force, I find it hard to accept that short didactyl arms, even very well-muscled and robust didactyl arms, were all that useful in predating upon multi-ton herbivores, but this is not to say that the arms were useless. As Lipkin and Carpenter argue, the pathologies present in T. rex forelimb and pectoral bones indicate that they were indeed subjecting their arms to extensive forces.
Digital modelling of a T. rex skeleton is used by Kent Stevens and colleagues to reconstruct possible sitting and resting poses in the animal. Relatively little technical work exists in which authors have tried to depict the resting and sitting postures of dinosaurs, and understandably there is little opportunity to test ideas on this subject. Lambe (1917) depicted a possible resting posture in Gorgosaurus and several artists have followed suit, but these reconstructions were nothing more than artistic endeavours. The beauty of the computer-generated work that Stevens and colleagues present is that it allows the digital manipulation of accurately proportioned models that incorporate data on ranges of motion, gravity and loading. So we get our first scientifically rigorous look at what a squatting and resting tyrannosaur might look like. Newman's (1970) idea that tyrant dinosaurs might have used their strong arms to help steady themselves when rising from a recumbent posture is testable, but while it might work it appears more awkward than does the possibility that the release of the energy stored in the Achilles tendons allowed the animal to stand without resorting to this. An accompanying presentation included on the CD-ROM that comes with the book illustrates the ranges of motion permitted by the model, and excellent animations show what it is capable of [one of the stills is shown here, from Kent Stevens's website]
Phil Manning provides an overview of new ideas on footprint dynamics and how to study them and, in his second contribution in the book, Peter Larson provides an atlas of T. rex skull bones. The accompanying photos (on the CD-ROM) are excellent and useful (if you work on theropods), but are marred by the total absence of scale bars. Hans Larsson looks briefly at palatal kinesis, with the evidence for this hinting at the possibility that the kinesis so typical of birds may have originated deep within Tetanurae. Given comments made about such animals as allosauroids and coelophysoids elsewhere in the literature, there are certainly indications that cranial kinesis was present throughout the evolutionary history of the theropods [UPDATE: this was written before Holliday & Witmer (2008) was published: see discussion here] [CM 9380, T. rex holotype, shown here].
Ralph Molnar's article complements his previous papers on cranial morphology and mechanics in T. rex (Molnar 1991, 2000). These articles are all well-written, well illustrated and pretty convincing, and the new paper included here provides a detailed discussion of the inferred cranial musculature of T. rex. One interesting area of conflict that arises from Molnar's reconstruction concerns the soft-tissue anatomy of the antorbital fossa in T. rex, and by inference that of all theropods and perhaps of all archosaurs with large antorbital fossae. Based on the surface texture of the bone within the antorbital fossa, Molnar reconstructs T. rex with an immense pterygoideus anterior that fills the cavity and anchors to the ventral, anterior and dorsal margins of the fossa [see figure below, by Ralph Molnar]. This is the 'conventional' reconstruction for theropods. However, it's flatly at odds with Witmer's proposal that the whole of the antorbital fossa was occupied by a gigantic antorbital sinus (see Witmer 1997, fig. 6): Witmer still, of course, depicted the pterygoideus anterior musculature as anchoring in the antorbital fossa, but as being far smaller and far more ventrally restricted. Molnar is well aware of this conflict and suggests that histological examination of the fossa margins might resolve this problem. He also suggests that different archosaurs might have differed in the extent of the pterygoideus anterior. One might predict that an animal such as T. rex, specialised for power-biting and well known for possessing hypertrophied cranial musculature, might represent an extreme example at the 'muscular' end of the scale.
Molnar's article will also be of use to those interested in reconstructing the life appearances of dinosaurs given that it is one of very few works that shows exactly where the tympanum belongs [see above]. Artists apparently lacking in guidance have often positioned the ear on the side of the neck, posterior to the depressor mandibulae, or even within the laterotemporal fenestra, but it should in fact be located anterior to the depressor mandibulae and just ventral to the posteroventral part of the squamosal. One unfortunate problem does afflict this paper, and that is its formatting: several of the figures are far removed from the associated text of the article and have been placed adjacent to the references.
Bruce Rothschild and Ralph Molnar look at pathologies, of which a great many are known from tyrant dinosaurs. This is a useful survey, but questions might be raised as to whether the aetiologies they propose are the most likely ones. They suggest, for example, that healing fractures observed in gastralia present evidence that tyrants could survive and recover from accidental falls. Well, maybe, but falling flat on your belly is not the only way in which you might receive broken gastralia (interactions with prey and conspecifics are just as likely).
Greg Paul's paper on 'the totally extreme lifestyles and amazing habits of the gigantic mega-awesome tyrannosaurid superhyperpredators of the Late Cretaceous of North America and Asia' (or something like that) essentially consists of a series of informed speculations that, while appearing reasonable based on what we know, will be annoying to some given his habit of making unsupported assertions. He provides an extended critique on tyrant dinosaur hindlimb anatomy, limb posture and running speed, and he continues to disagree strongly with those who argue that T. rex was limited to elephant-like speeds. New work indicates that tyrannosaurs grew quickly and died young (as did, as a generalisation, all dinosaurs it seems), a discovery that leads Paul to imagine that tyrant dinosaurs were 'chronically living closer to the edge of danger and death'. In other words, that they lived reckless, dangerous lives where caution was thrown to the wind: more like salmon than elephants, notes Paul. The comparative work presented here on the skulls of the different tyrants is useful.
John Happ describes an exciting Triceratops specimen that many will already be familiar with because of its appearance on television documentaries: it would appear that a large predator with a very powerful bite grabbed hold of one of the animal's brow horns and bit it off, and also damaged the side of the frill with a bite. The Triceratops survived, but appears to have suffered from osteomyelitis following the attack. By reconstructing the angle of attack employed by the predator, Happ shows how the Triceratops and its attacker (T. rex is the only candidate) engaged in face-to-face conflict. The unknown factor is how common interactions of this sort were. Paul notes in his paper that this was quite likely an attack gone wrong, as attacking an elephant-sized horned herbivore from the front and biting its horns is probably not a good idea.
In a long-awaited contribution, Thomas Holtz provides a formal, critical answer to John Horner's proposal that T. rex was an obligate scavenger, unable to kill live prey and destined for a life of wandering the Cretaceous landscape ever in the quest of decomposing carcasses. It's difficult to be sure whether Horner really believes his own hypothesis: one gets the impression that he likes promoting it because it earns him lectures and TV appearances, and surely he knows that it's not really a defensible point of view. Horner's claim that T. rex had 'beady little eyes' (and hence poor eyesight) is shown to be incorrect, and Holtz also tackles claims that hindlimb proportions and tooth morphology support a scavenging lifestyle when the data shows that they don't. Holtz reviews the evidence for predatory behaviour in giant tyrant dinosaurs, concluding (like Paul) that they were most likely canid- or hyaenid-like 'jaw-based' predators, able to resist significant twisting and skull loading when grabbing prey, and also able to withstand occasional contact with bone.
The volume ends with a look at the role of T. rex in popular culture, by Don Glut. From the art of Charles Knight to the Zallinger mural and its role in sci-fi stories and movies, T. rex has been a constant presence, and one invariably portrayed quite inaccurately. This continued until recently (the BBC's T. rex in Walking With Dinosaurs is one of the least accurate modern renditions of this animal: it's shown here), but has finally begun to change. Brief contributions by other authors are also included elsewhere in the book and look at such topics as the age of T. rex-bearing beds, and at the discovery and taphonomy of specific individuals.
Tyrannosaurus rex: the Tyrant King contains some very interesting contributions, and everyone involved in tyrant dinosaur, or Cretaceous theropod, research will want at least some of the papers that are included; Molnar's and Holtz's chapters in particular are sound contributions to the literature, and it is good to see the studies by Happ and Stevens et al. in print. But the book also incorporates some unusual and problematic articles that, one cannot help but assume, might have appeared here because they could not be published elsewhere. A phylogenetic perspective on the book's subject is notably absent, and - given the controversial and very interesting claims about the validity of Nanotyrannus and additional Tyrannosaurus species - it's unfortunate that nobody submitted a paper that provided a rigorous, empirical analysis of T. rex systematics. This is partly because another special meeting on tyrannosaurs was held at the Burpee Museum of Natural History just a few months after the Hill City meeting, and for whatever reason this is the one where the phylogenetic papers were presented. I also found the lack of abstracts from the contributions unhelpful (particularly in writing this review, when access to brief summaries would have been very helpful!) and, as is unfortunately par for the course for IUP volumes, the editing is not too hot and typos are easy to find.
Peter Larson and Kenneth Carpenter (2008). Indiana University Press, Bloomington and Indianapolis, 435pp. ISBN 978-0-253-35087-9, $49.95 (hardback, includes CD-ROM).
This book review originally appeared in the Palaeontological Association Newsletter 69: available (for free download) here and is reproduced with permission.
Refs - -
Bakker, R. T., Williams, M. & Currie, P. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1 (5), 1-30.
Brochu, C. A. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Journal of Vertebrate Paleontology 22, Supplement to Number 4, pp. 1-138.
Carpenter, K. & Smith, M. 2001. Forelimb osteology and biomechanics of Tyrannosaurus rex. In Tanke, D. H. & Carpenter, K. (eds) Mesozoic Vertebrate Life. Indiana University Press (Bloomington & Indianapolis), pp. 90-116.
Carr, T. D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology 19, 497-520.
Charig, A. J. 1972. The evolution of the archosaur pelvis and hind-limb: an explanation in functional terms. In Joysey, K. A. & Kemp, T. S. (eds) Studies in Vertebrate Evolution. Oliver & Boyd (Edinburgh), pp. 121-155.
Holliday, C. M. & Witmer, L. M. 2008. Cranial kinesis in dinosaurs: intracranial joints, protractor muscles, and their significance for cranial evolution and function in diapsids. Journal of Vertebrate Paleontology 28, 1073-1088.
Lambe, L. M. 1917. The Cretaceous theropodous dinosaur Gorgosaurus. Memoirs of the Geological Society of Canada 100, 1-84.
Molnar, R. E. 1991. The cranial morphology of Tyrannosaurus rex. Palaeontographica Abteilung A 217, 137-176.
- . 2000. Mechanical factors in the design of the skull of Tyrannosaurus rex (Osborn, 1905). Gaia 15, 193-218.
Newman, B. H. 1970. Stance and gait in the flesh-eating dinosaur Tyrannosaurus. Biological Journal of the Linnean Society 2, 119-123.
Witmer, L. M. 1997. The evolution of the antorbital cavity of archosaurs: a study in soft-tissue reconstruction in the fossil record with an analysis of the function of pneumaticity. Journal of Vertebrate Paleontology 17 (Supplement to No.1), pp. 73.
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Great review!
"...'morphodynamic compensation' explains how the diminutive forelimbs of these theropods were an accidental consequence of genetic investment in the proportionally gigantic skull.".
Following this hypothesis, and reversing the investiment, we can assume that the skull of Deinocheirus would be diminutive if not atrophic (explaining its absence in the fossil record). ;-)
Could T-rex grab prey with its tiny arms, move neck and deliver a killing bite?
My vision is that 1) fingers and forearms would snap and 2) basically the neck was too short to bite an object held in forepaws, much like a man cannot bite his own chest.
How flexible was T-rex neck region?
As an evolutionary biologist, I think it is a lie that there is a 'morphodynamic compensation' meaning that growth of one body part must somehow automatically diminish another body part.
So, would a tiger have weak claws because it has strong jaws?
Thanks for the review!
Personally, I've never been a fan of the Walking With Dinosaurs T-rex; for some reason, I didn't find it aesthetically appealing, especially where the head was concerned. On the other hand, the Jurassic Park T-rex remains my favourite movie/TV reconstruction to date.
From a development genetics perspective, I have not the slightest idea how "morphodynamic compensation" might possibly be able to work.
Strong jaws? A tiger? I have stronger jaws than a tiger. The tiger just has better cutting teeth.
It was deliberately modeled after Horner's (mis)conceptions.
Excellent article Darren. The information given was rather interesting.
"Horner and Lessem's popular book The Complete T. Rex where this notion is mentioned as one of Robert Bakker's pet hypotheses"
In the book, Horner actually just about says verbatim "the only thing Bakker is good for is saying stupid stuff to get people angry and have them disprove his ideas". Yeesh.
"Horner's claim that T. rex had 'beady little eyes"
Interestingly, this sounds a lot like Larry Martin's claim once the feathered dinosaurs came out that "Archaeopteryx couldn't have run on the ground because it had claws way at the ends of its wings, which would drag on the ground" or something like that.
Anyway, I found Horner's one claim that tyrannosaurs were scavengers like turkey vultures because they had good senses of smell somewhat laughable. Yes, its true that scavengers do have good senses of smell, but realize that vultures, condors, and New World vultures are about the only obligate scavengers out there, mostly because they are energy-efficient when they fly. And there are numerous predators out there who have excellent senses of smell...dogs for example, just look what they use bloodhounds for. Of course, saying that T-rex would turn its nose up at a Triceratops carcass is ludicrous too.
"Nanotyrannus and additional Tyrannosaurus species"
Also note that no one started considering "Jane" a juvenile T-rex until Horner came out and said it. Horner is the most anti-Nanotyrannus person there is, that would be like asking a creationist if a fossil provides evidence of a certain evolutionary theory. What needs to be done is the fossils need to be reviewed by a third party, not Bakker, not Horner.
I too have always thought of tyrannosaurids as the canines or hyenas of the Cretaceous. They weren't incredibly fast, but I have read in some sources that they would have been good endurance runners. They had highly specialized feet for a cursorial lifestyle, and the forearms were mostly useless in the attack (canines have just about the carnivoran equivalent of hooves on their forefeet, and tyrannosaurs...well, need I say more). They have an excellent sense of smell, and they also have a bone-crushing head which gets most of their business done.
"T. rex has been a constant presence, and one invariably portrayed quite inaccurately."
So...out of curiosity, what is the most accurate T-rex out there in pop culture?
"T. rex is the only candidate"
That has always struck me as off to. Why was T-rex the only large predator in Maastrictian North America? Unless Nanotyrannus does indeed turn out to be a separate species, the next large carnivore in the area is a troodont (ignoring the oviraptorosaur and ornithomimid because they seem to be more small animal eaters, omnivores, or herbivores rather than potentian hunters of larger animals). Compare that to the Morrison, where you have Torvosaurus, Allosaurus, Ceratosaurus, Tanycolagreus, Marshosaurus, Stokesosaurus (possibly the same as Tanycolagreus, but still), Ornitholestes, Coelurus, even a couple bones of ?Elaphrosaurus have been noted.
Speaking of T-rex and predators of the Maastrictian, I recently read Horner's book on re-engineering "non-avian dinosaurs" from chickens. He inserts his theories in there a lot, not least of which is the idea that troodonts were the apex predators of the Late Cretaceous. Not dromaeosaurs, troodonts.
Metalraptor:
Hmm. Interesting question. There are no post-Campanian Deinosuchus known, are there?
100 Years of Tyrannosaurus rex is the best volume hands down ever written about Tyrannosaurus rex. The one thing I wished this volume would have covered is Tyrannosauroids in general.
True, it has the Juvenille/Nanotyrannus debate, which is a very good subject. However, it needed a section to cover on t-rex ancestory, expecially something about the earliest feathered tyrannosaurs coming out of China. Overall this volume is a must for Theropod specialists and dinosaur fans alike. It makes the other Tyrannosaurus rex books e.g.s Horner and Lessem's and Larson's previous volume look "amateur". Maybe a new tyrannosaur book in the future may address the topics that were mentioned.
Thanks for the review... what a great way to ruin my productivity for the morning!
On a personal level, I'm always jazzed to see Dr. Holtz mentioned in blogs I read. I took several of his classes at UM, and he's a great and enthusiastic professor =D
Darren, did the book just hit the UK? It's been out here for like a year--I wrote a blog post a long time ago about Holtz's paper WHICH I LOVE.
EAT IT, HORNER!!!
*ahem* Sorry. Great review. I find many of the papers questionable, especially the Lockley paper, which is just wierd.
David Marjanovic wrote:
Really? I haven't read any data on tiger jaw strength, but I have done some work on lion jaws, and they are pretty darn strong. I'd think that tigers (being similar, but bigger) would have had pretty strong jaws too.
Metalraptor wrote:
If tyrannosaurs were carnosaurs, I would have an easier time believing that these were adaptations for cursoriality. Since tyrannosaurs evolved from smaller coelurosaurs, it is possible that many of the supposed adaptations for running, are really just evolutionary holdovers from more cursorial ancestors. It reminds me of Sarcosuchus; an animal that secondarily evolved a robust jaw, from longirostrine ancestors. Without knowing its phylogeny one might be lead to believe that it was a brevirostrine crocodyliforme that evolved a more piscivorous lifestyle, rather than the other way around.
Horner's scavenger theories about T-rex are, and have always been indefensible, because a large, terrestrial scavenger is both impractical and unprecedented. You may be right in the idea that he really doesn't believe what he says, since he's contradicted himself on more than one occasion.
As far as what "looks fairly accurate to me" are the one Tony McVey had done years back: http://www.menagerieproductions.com/fig/fig.html (scroll down to bottom of page).
I live in NJ in the US and remains of dryptosaurus which they say was a pretty good size, so I wonder how far they roamed (and if they ever found any more remains)
Good review, too...
Fine, but then, nobody has ever made that claim as far as I'm aware.
The textbook explanation is that the niches for intermediate-sized predators were taken up by intermediate-sized, juvenile and subadult T. rex. Which makes sense to me.
Also, everyone seems to agree that Jane is not adult.
All I've read on comparative bite strengths (...naturally, all of it connected to T. rex...) says that most carnivorous mammals have surprisingly pathetic bite strengths (unless compared to Komodo monitors or Allosaurus or suchlike). Or in other words, we have surprisingly high bite forces. Well, not so surprising considering that most of our food doesn't just need mere cutting, and that we're basically frugivores that switched to nuts and tubers as staple food. Paranthropus was just the extreme. We, too, have much thicker enamel than other apes, much more molariform premolars, and so on.
Excellent article
"the BBC's T. rex in Walking With Dinosaurs is one of the least accurate modern renditions of this animal"
At the risk of opening a can of worms, what was wrong with it?
I've heard Jack support this idea a lot. I don't think he really believes it. I think his intentions are to get people to think through why they believe things and think through the data that supports it. I don't think the goal is more lectures or TV appearances.
"Also, everyone seems to agree that Jane is not adult."
Never said Jane wasn't an adult.
"I've heard Jack support this idea a lot. I don't think he really believes it. I think his intentions are to get people to think through why they believe things and think through the data that supports it. I don't think the goal is more lectures or TV appearances."
I've been to the Museum of the Rockies when they opened up their new Hell Creek exhibit. The whole exhibit was Horner-central, they showed T-rex as an obligate scavenger and they didn't even show the other side of the debate.
One bit of evidence Horner has never mentioned that puts the scavenger/predator debate to rest is the Edmontosaurus on display at the Denver Museum that has a a few of the top of the tail vertebrae missing that fit the cookie cutter bite mark of a t-rex. Ken Carpenter showed this was a pathology that healed. This bit of evidence is one that Horner seems to never mention, as far as arguments go againsts his scavenger idea.
As I recall from Horner's books he states T-rex is his least favorite dinosaur. Even though he maybe antitrex, I think his goal as someone else mentioned is to make the public think for themselves.
Excellent review. You hit the nail squarely on the head, and much of what you said agrees with my review in the latest issue of Palaeontologia Electronica (if I may be permitted this bit post-hijacking). I'm glad I wasn't the only one completely puzzled by the whole idea of 'morphodynamic compensation.' So many buzz-words that it makes my head hurt!!!
Having spent some time trying to rebuild the 'Walking with Dinosaurs' T-rex full size, I agree about its weirdness. Its posture was particularly strange, balanced on tippy-toe for some reason and a suffering from a scrawny pencil-neck. Our new version is basically a complete re-sculpt, based in part on information from this excellent book.
Many thanks to all for comments, glad you enjoyed the review. Some responses...
-- On forelimb function (see comments from Jerzy, number 2), it has been proposed by Ken Carpenter (and colleagues) that T. rex was perhaps able to 'latch on' with its short arms when attacking prey. Obviously, this can only happen at very close range. A small object clutched to the chest is almost certainly going to then be out of range of the jaws, while a large object will be in range of the jaws anyway, thereby making forelimb prehension useless.
-- 'Morphodynamic compensation': with all respect to Martin Lockley and colleagues, I have yet to see any positive comments on this hypothesised evolutionary mechanism and my geneticist friends tell me that it's complete nonsense.
-- Zach (comment 11): no, the book has not only just come out on this side of the pond. My review has been out for months, and was submitted and written months earlier - remember it always takes a while for reviews to get published.
-- Why was T. rex the only big Maastrichtian predator? This is a good question. As David notes (comment 15), we have evidence showing that the different growth stages of T. rex acted as separate 'ecological species'. However, this was likely true of many (or all?) large theropods, so I'm not sure it solves the problem. For whatever reason, the Maastrichtian fauna in western North America seems to have been impoverished: look at hadrosaurid and ceratopsid diversity compared to that of the Campanian. This has been linked to a turnover in environmental and ecological conditions, and the late Maastrichtian western North American fauna seems to have been unusual compared to the other faunas of the Late Cretaceous.
-- What was wrong with the WWD T. rex (comment 16)? Err: everything. It's horrible, and whoever created it looked only briefly at the real animal. Philip (comment 21) mentions some of the problems. I could write a whole essay on how bad that model is, but I'll just concentrate on the head, as it's particularly offensive. The WWD animal doesn't really have the flaring cheeks of T. rex, it lacks the little cheek horns, its teeth are widely spaced and essentially homodont (T. rex was markedly heterodont, with closely packed incisiform teeth and long teeth in the maxilla), its snout slopes down such that the snout tip is 'stepped down' relative to the region in front of the eyes, it has a totally imaginary thickened rim around the edges of the upper jaws, its nostril is located on the top of its snout as if itâs a hippo, it has a weird, sunken antorbital area that is in the wrong place, it has a horizontal ridge running ventral to its eye (no such structure in T. rex), it has a great big horn right over its eye (as opposed to the blunt preorbital hornlet and massive, rounded postorbital boss present in the real thing) and the back of its head was complete fiction which made it look at if the head was somehow a separate entity from the unmuscled, scrawny neck. The skull of T. rex is a shapely, sophisticated thing that we have excellent information on: the WWD thing was a total monstrosity. For those who don't know, I would like you to note that (with Dave Martill, allegedly), I wrote a book called Walking With Dinosaurs: The Evidence. Unfortunately I wasn't allowed to be too critical of any of the WWD stuff, but I did say some vaguely negative stuff about the T. rex on p. 149.
Sorry for the confusion -- I never implied you say it was! :-) My point is that, if Nanotyrannus is separate from Tyrannosaurus and if Jane belongs to Nanotyrannus, then Nanotyrannus must have been pretty big when adult -- and therefore not really an intermediate-sized predator. We'd end up with two big ones and still no intermediate ones.
You're right about that. I was talking with some of the staff at the CMNH, and they were thinking that the type specimen of Nanotyrannus wasn't fully grown either. It was more of a sub-adult, however, than a juvenile, so the animal that came out of this evolutionary pathway probably looked like a tyrannosaurine tyrannosaur trying very hard to be an albertosaur. Not to mention there were a couple features on the skull that showed that whatever this creature was, it would not grow up into a T. rex (maybe a T. lancensis or something, but probably not a T-rex).
What it seems like to me (this is just speculation), is that T-rex and Nanotyrannus shared a common ancestor, perhaps somewhere on the tyrannosaur famiy tree past Daspletosaurus. Its sort of like chimps and humans, our infant forms look somewhat similar, but the adult products are radically divergent. T-rex probably went one way, taking the trends of its daspletosaur ancestors to an extreme, while Nanotyrannus went into the niches abandoned by the albertosaurs (who seem to be either uncommon or extinct in Maastrictian times, I'll have to check).
Another interesting debate going on with Tyrannosaur systematics is the issue of the Tarbosaurus bataar and Tyrannosaurus rex. (Carpenter 1992) feels that Tarboosaurus bataar is so similar in morphology to Tyrannosaurus rex that it should be renamed Tyrannosaurus bataar. It only has a few minor features such as a few extra teeth and a little more gracile build. I agree with him on this one, a good analogy for this comparison would be Alligator mississppisiensis and Alligator sisensis, both are very similar but one has only minor differences.
Tyrannosaurus bataar is probabley the direct ancestor Tyrannosaurus rex as Currie has stated. Daspletosaurus although considerd by many to be the direct ancestor of t-rex does not share the same overall morphological similarity that Tyrannosaurus(Tarbosaurus)bataar does.
On Nanotyrannus and the distinction of Tarbosaurus from Tyrannosaurus, you should see...
Currie, P. J. 2003a. Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences 40, 651-665.
- . 2003b. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48, 191-226.
- ., Hurum, J. H. & Sabath, K. 2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 48, 227-234.
Hurum, J. H. & Sabath, K. 2003. Giant theropod dinosaurs from Asia and North America: skulls of Tarbosaurus bataar and Tyrannosaurus rex compared. Acta Palaeontologica Polonica 48, 161-190.
[NOTE: Acta Palaeontologica Polonica is OPEN ACCESS, FREE TO ALL]
Currie (2003a) regarded Nanotyrannus as a distinct species, albeit one closer to T. rex than to anything else. So if it's a juvenile (as everyone now agrees), the holotype was still destined to grow into a large, T. rex-like animal. As for Tarbosaurus, most tyrant dinosaur workers now seem happy to regard it as 'different enough' from T. rex to warrant generic separation, and indeed they are pretty different (Hurum & Sabath 2003). Note that some phylogenies recover Tarbosaurus as closer to Alioramus and Daspletosaurus than to T. rex... in fact, this is what I got in my PhD work.
In that case, Tarbosaurus would simply be an incredibly example of parallelism, yes?
Great review!
As for the differences between "normal" theropod guilds and Campano-Maastrichtian Asiaamerican ones; that is a theme of my presentation last Monday at Saskatchewan and this June at NAPC.
Paleontological conventions aside, mustn't the null hypothesis, for any two specimens from different mesozoic strata, be that they came from different species? How often do we find modern creatures that are defensibly of the same species as a fossil specimen from two million years ago?
David M., I anticipate, will point out that "species" is formally undefined, so that an ornithologist and an entomologist use the word to mean very different things than would a paleontologist, or one another. Still, aren't we awash in modern tetrapod lineages that are distinguishable only by features not preserved in fossils? Is the mesozoic megafaunal definition of "species" (assuming one could be elucidated) consciously very different from that for extant taxa? Are there really no characters that show progressive change in T. mumble over three million years?
On the subject of "morphodynamic compensation", it was my impression (without having read the book) that this was strictly related to bipedal balance, and not an appeal to some mystical principle. That is, each kg of muscle on the arm implied a half kg that could not be added to the skull without adding a corresponding half kg to the tail at the same time. It must not have been easy to grow two (very different) ends of such a large animal at the same rate.
I would suggest that the null hypothesis for alpha taxonomy in fossil species is based around the morphological species concept, rather than one that is explicitly stratigraphic. At least, that's how I've attempted to use it in my own work... (That there are several different formulations of the species concept is not necessarily a problem - different disciplines tend to use the one(s) that apply to the questions they are interested in.)
Given a number of specimens which are from more than one horizon, a morphospecies-based approach would be to consider them to be one species only if the range of variation represented by the fossils lies outside the range that could be reasonably interpolated for a single species. Personally, I don't think stratigraphy should come into it - if you can convince yourself that there is more than one species present, then all combinations of stratigraphy and species numbers are possible, so it's not like stratigraphy is going to tell you anything that you can't work out just by examining the pattern of morphological variation. Unless you do your alpha taxonomy by assuming that species have particular temporal spans, which I think is an unnecessary burden.
I wrote:
I wish you could edit your own posts... what I meant, of course, is that a morphospecies-based approach would be to consider them to be multiple species only if the range of variation represented by the fossils lies outside the range that could be reasonably interpolated for a single species.
But I'm curious to hear what others think of this question.
I'm very much with Colin on this one: fossil species are 'morphological species'. Obviously, we cannot test the possibility (as we can with extant taxa) that morphologically similar animals (like, say, all the individuals referred to T. rex) actually differed enough (in genetics or soft-tissue anatomy) to warrant separation. Some extant species are essentially indistinguishable osteologically, and some fall within the range of osteological variation seen in certain other species. Palaeontologists have often wondered about this subject: Ralph Molnar includes a discussion of it in his paper in Dinosaur Systematics.
Because we rely on this morpho-species concept, we have to totally ignore stratigraphy and geography. If you find vertebrates that are morphologically alike and share the same diagnostic skeletal features, you have to consider them conspecific, even if one is from the Triassic of S. America and the other from the Cretaceous of Europe (the closest that any dinosaur comes to this is the archaeotrogonid Archaeotrogon venustus, which is supposed to have been around for about 14 million years). I would argue that we cannot make the assumption that species only ever hang around for x million years. Having said all that, dinosaur morpho-species do tend to be restricted to a span of a couple million years at most.
Oh - and, how much variation you're prepared to accept within a morpho-species is still entirely subjective. We're mostly happy with all those T. rex individuals belonging to one 'species', but they exhibit a range of variation that exceeds that of some (not all, but some) extant species.
Darren:
I'm less than entirely up to date with dinosaur literature, so I'll ask, out of curiosity... How quickly is 'quickly' and how young is 'young'? (I'm interested in ballpark figures, obviously.) And how is it with indeterminate growth in dinosaurs - is there any evidence for that?
Nooooo.
I'll point out that "species" is formally undefined, so that two ornithologists use the word to mean very different things than one another... and as themselves at different stages in their careers... and in different places in the same description... and...
Depending on the definition, there are between 101 and 249 endemic bird species in Mexico.
Dartian;
The oldest known T.rex specimen is the Field Museum's Sue, aged 28 years at time of death. Adult size is reached in twenty years. See
Gigantism and comparative
life-history parameters of
tyrannosaurid dinosaurs
Gregory M. Erickson, Peter J. Makovicky, Philip J. Currie,
Mark A. Norell, Scott A. Yerby & Christopher A. Brochu
in NATURE VOL 430 12 AUGUST 2004
Evidently I should have added to "or one another" another clause, "or themselves, five minutes later". It raises the question of why anybody bothers discussing speciation in T. mumble at all. Is it sensible to talk about progressive change within a species? Is there evidence for it, here?
The need to match growth rates of the tail and the snout, as indicated by the pathetic arms, suggests that the match must sometimes have failed, resulting in some individuals that bumped their noses rather more than they would have liked. This seems like the foundation for a Pixar movie.
Mostly just out of tradition... Triceratops might be common enough for some kind of population biology, which would make a few interesting species concepts applicable, but for Tyrannosaurus it probably doesn't make sense to recognize anything but clades.
Oh, and, the ICZN has a requirement that a genus cannot exist without containing at least one species. It doesn't allow us to have just Tyrannosaurus. The PhyloCode will.
Why not?
No idea.
Darren, I just happened to notice your run-down on all the inaccuracies in the "W.W.D." T-rex (my feelings about that series are decidedly mixed, and as a reasonably well-informed layperson I've noticed that these programs play fast and loose with paleontological facts.) Like Spielberg and "Jurassic Park", the makers of these shows hire paleontologists as advisors, but disregard their input for "dramatic" or equally misguided reasons. Defeats the whole purpose, and poorly serves the public.
"I wrote a book called Walking With Dinosaurs: The Evidence. Unfortunately I wasn't allowed to be too critical of any of the WWD stuff, but I did say some vaguely negative stuff about the T. rex on p. 149."
Your objections were couched very diplomatically, I must say.
Thankyou for writing a book I have read time and again!
Thanks for the reference, Your Name's Not Bruce? (Are you from Oz, BTW?). Will look it up.
Hmm. It's not that young, then. About the same age when male African elephants reach full sexual maturity.
Does anyone have similar info on growth/maturity in sauropods?
Thanks, Robert, for the positive comments about the WWD book. One bit in particular is appalling: 'The end of an era' on pp. 171-172. I didn't write it.
On life history and longevity in T. rex, perhaps the most interesting thing is that these large animals did not live for decades and decades. In fact, they seem to not to have lived beyond their 30th birthdays. Erickson et al. (2004) is available, for free, here.
As for growth and maturity in sauropods, I will save myself some time and direct you to the comment here.
Coming to inaccuracies in WWD, dinosaurs seem to spend a lot of time standing, roaring and waving, like animators didn't know whata dinosaur could do.
I would also enjoy some more colors. I love one wonderful, green and brown camouflaged T-rex stalking Edmontosaurus in one National Gegraphic magazine.
Thanks for the refs, Darren. I have some comments on this subject, but they'll have to wait for a day or two.
Jerzy:
At least the carnivorous dinosaurs played fair: they always roared loudly both before and during an attack and thus warned their prey. (Hmm. Come to think of it, no wonder that they went extinct.)
"and its familiarity and popularity might instead be argued to be coincidental, the result of its relatively early discovery (it was named in 1905) and of its status as one of the world's largest predatory dinosaur."
Also an AWESOME name...
Darren:
It's interesting indeed, although it should be kept in mind that Erickson et al. (2004) have provided evidence for how long the tyrannosaurs' usual lifespans were, rather than demonstrated how long their potential maximal lifespans could be. On this latter subject they do not say much; unless I've missed something, they only say - in one somewhat subjective-sounding sentence - that 'Sue' "showed evidence for prolonged senescence in the form of conspicuously narrow pericortical growth-line spacing"* (p. 773). But they certainly at least hint at circa 30 years being the oldest that any tyrannosaur ever got.
* They also do not, unfortunately, present much comparative data on how reliably senescence can be established from skeletal material in extant amniotes, particularly birds and crocodilians. Does anyone know how senescence shows in archosaur skeletons? (In mammals, tooth wear is often a good indicator of advanced age, but that's not really applicable to archosaurs.)
Typical lifespan and theoretical maximum lifespan are, of course, different things. Most small modern passerines, for example, have very short average lifespans. David Lack, IIRC, showed that the average life expectancy of a robin Erithacus rubecula in Britain is only about one year. Few individuals make it past 2-3 years. But some do, and they may beat the odds in quite spectacular fashion: the oldest known non-captive E. rubecula in Europe was over 17 years, according to the Euring's bird longevity records!
That Euring list really is quite interesting reading. It shows that ages of 30-40 years - and remember that these are records of wild, not captive, birds - are not that uncommon among birds that only weigh a few kilograms, or even less. Clearly, many/most birds have at least the potential to live a very long life. 'Very long', that is, when compared to mammals. Longevity is correlated with body size in both birds and mammals, but birds are on average much more long-lived: a bird may live 2-2.5 times longer than a similar-sized mammal* (Holmes et al., 2001). Why this is the case is not yet well understood, but it has probably little or nothing to do with either 'endothermy' or with the fact that most birds can fly: 'ectothermic', non-flying amniotes (think tortoises) also reach higher maximal ages than similar-sized mammals. So perhaps the real question is rather: Why are mammals so short-lived?
* Among mammals, it's almost only the very largest species that are capable of living for many decades. Not even the most pampered and well-kept pet cat or dog will live for 40 years (and very likely not even anywhere close to 30), but a pet parrot very well might (Brouwer et al., 2000). The exceptions that prove the rule: naked mole-rats Heterocephalus glaber, which may live at least 28 years in captivity (Buffenstein, 2005), and echidnas, which may live 50 years both in the wild and in captivity (Hulbert et al., 2008), are exceptionally long-lived mammals for their body size. And, of course, we humans are disproportionately long-lived too.
Which brings us back to the tyrannosaurs. They are phylogenetically very, very close to birds (indeed, birds are, of course, dinosaurs). Why were they then, if Erickson et al. are correct, physiologically incapable of reaching similar advanced ages that modern birds do? Were there never, ever a few lucky T. rex individuals that made it, say, to their eighties or nineties? If that is the case, then tyrannosaurs, and probably other dinosaurs as well, were more similar longevity-wise to modern mammals than to birds (as also noted by, e.g., Ricklefs, 2007). But why should a shorter lifespan have evolved in their, and in the mammalian, lineage?
References:
Brouwer, K., Jones, M.L., King, C.E. & Schifter, H. 2000. Longevity records for Psittaciformes in captivity. International Zoo Yearbook 37, 299-316.
Buffenstein, R. 2005. The naked mole-rat: a new long-living model for human aging research. Journal of Gerontology: Biological Sciences 60A, 1369-1377.
Erickson, G.M., Makovicky, P.J., Currie, P.J., Norell, M.A., Yerby, S.A. & Brochu, C.A. 2004. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs. Nature 430, 772-775.
Holmes, D.J., Flückiger, R. & Austad, S.N. 2001. Comparative biology of aging in birds: an update. Experimental Gerontology 36, 869-883.
Hulbert, A.J., Beard, L.A. & Grigg, G.C. 2008. The exceptional longevity of an egg-laying mammal, the short-beaked echidna (Tachyglossus aculeatus) is associated with peroxidation-resistant membrane composition. Experimental Gerontology 43, 729-733.
Ricklefs, R.E. 2007. Tyrannosaur ageing. Biology Letters 3, 214-217.
David:
I'm not sure if I understand that correctly... Isn't that a moot point, as the PhyloCode does not govern the establishment or precedence of species names? That job would be left to the ICZN and the other traditional codes so that even in the future, every 'genus'-level name must still be attached to a 'species'-level name. Is this not how it's planned?
While I'm at it: David, you know the PhyloCode better than pretty much anyone here. Could you please elaborate a little on how this division of labour between the PhyloCode and the traditional codes is supposed to work in practice? For example, according to Article 21.2. of the PhyloCode, "the first part of a species binomen is not interpreted as a genus name but instead as simply the first part of the species name". Fine. But according to the ICZN and the other traditional codes, the first part of the binomen would be interpreted as a genus name. Is here not an obvious source of conflict and/or confusion?
Some quick and entirely random comments on the nice longevity comments made above by Dartian...
-- Senescence in reptiles is sometimes indicated by a slowing/absence of tooth replacement. There are old alligator and monitor lizard specimens where the alveoli have started to close as tooth replacement has slowed or stopped. Gnarly skull texture can also develop in extreme old age.
-- Long life in small mammals: I recall reading that bats are atypically long-lived compared to similar sized mammals. A quick check shows various microbats living to age 30, with 15-20 years being very common in some species (like European long-eared bats).
-- Domestic cats: there are several pet cats that lived to 30 and beyond. Ma, from Devon in England, lived to 34 and Puss... err, also from Devon, apparently, lived to 36. There is also a captive bobcat that got to age 34 before being euthanised.
-- Back to Mesozoic dinosaurs: remember that, UNLIKE MAMMALS, dinosaurs seem to have been r-selected animals where large clutches and rapidly growing juveniles could quickly replace adults. This doesn't explain the comparatively short lifespans of animals like Tyrannosaurus, but it's consistent with them.
Darren:
Very interesting! (Do you have references handy?) So teeth are informative also in non-synapsids, then. But how is it with the toothless birds? For example, if you had the skeletons of a normal, 2-year old robin and a one-in-a-million-exceptional, 17-year old robin, could you tell them apart?
Regarding bats: good call, they live long. Or rather, they can maximally live about as long as similar-sized birds.
Regarding cats: I've heard about those extremely old domestic cats, but the AnAge website (which, incidentally, has plenty of interesting data and references on animal longevity) is of the opinion that most, maybe all, reports of +30-year old domestic cats are insufficiently documented. But it agrees on the bobcat living past 30 years.
I'm not disputing that; I'm just wondering why having a short lifespan would be universally adaptive, regardless of the animal's strategy of reproduction. What are the adaptive 'benefits' of dying young?
Perhaps because they combine the disadvantage of a high metabolism â that is, an increased cancer risk â with the lack of whatever magic feature the birds have evolved to counter that. Birds get much less cancer than mammals; this also appears to be the reason why, among mammals, only the manatees have managed to have a number of cervical vertebrae other than 7, while the birds play around with it like crazy â the sloths (5 to 10 at face value) don't count, because they've shifted the ribs, not the vertebrae, as a rather stunning presentation showed at the SVP meeting last year. (In humans, shifts in the number of neck vertebrae has a high correlation with very-early-onset cancer, not to mention miscarriage.)
You mentioned the naked mole rat and the echidna as exceptionally long-lived; they also have very low metabolisms for mammalian standardsâ¦
Could be a trade-off: do you invest in repair or in reproduction?
Turtles need less repair and have more time for it; that might be why they manage to combine r-strategy and exceptionally long lives. Some wonder if turtles senesce at all (â¦unsurprisingly, the studies are still ongoing, and will keep being ongoing for decades!).
The PhyloCode does not recognize a category "genus". That's because it doesn't recognize ranks at all (you can optionally add them after the nomenclature has been done). So, the very concept of a "'genus'-level name" does not exist under the PhyloCode. Clade names are clade names are clade names.
So, the PhyloCode will allow people to define clade names directly by specimens*, and it lacks a requirement on whether clade names have to be grammatically singular or plural. So, it will allow you to define and publish names that will look like genus names but won't be valid genus names under any rank-based code.
You're of course right that this creates a conflict** between the PhyloCode and the rank-based codes. I just don't think that's a bad thing. To the contrary, I think the requirement that every organism must belong to a species â especially considering the complete lack of an anywhere-near-universally acknowledged, let alone anywhere-near-universally actually used, species concept â is rather silly, so we should stop pretending and make the issue visible.
If you think you can apply a species concept, say so, and tell us which one it is. If you think you can't, and if you think you can only apply uninteresting ones, you shouldn't be required to pretend, as the rank-based codes do.
Does this help?
Notes
* In most cases these will be the type specimens of already named species, and I expect that to happen for Tyrannosaurus. But that's not required. Recommendation 11.4A, emphasis added: "The use of specimens that are not types [of species named under the rank-based codes] as specifiers is strongly discouraged. This should be done only under the following two circumstances: 1) if the specimen that one would like to use as a specifier cannot be referred to a named species, so that there is no type specimen that could be used instead; or 2) if the clade to be named is within a species." Rec. 11.4B, emphasis added: "If a specimen that is not a type is used as a specifier in the first situation described in Rec. 11.4A, and a species that includes this specimen is subsequently named under the appropriate rank-based code, this specimen should be chosen as the type of the species name." â Article 11.4 says: "When a type specimen is used as a specifier, the species name that it typifies and the author(s) and publication year of that species name must be cited." Even this, however, this differs from the concept of "type species"; it's not even required that you acknowledge any taxonomic (as opposed to purely nomenclatural) validity of that nominal species.
** I agree that point 3 of the Preamble, "This code may be used concurrently with the rank-based codes.", although by no means the brazen lie as which it might appear at first sight, is a bit too general to fully account for every situation. In other words, it can get tricky.
Article 21 is about what to do when you really want to talk about a species in a PhyloCode context. My assumption above was that I don't, because all halfway interesting species concepts require some approximation to population biology, something that can hardly ever be done from the vertebrate fossil record; the concepts that are applicable (morphological, monophylyâ¦) are unnecessary when you can just name clades all the way down to the LITU.
Article 21.5: "Subsequent to a species binomen becoming available (ICZN) or validly published (ICBN, BC) under the appropriate rank-based code, the second part of the species binomen may be treated as the name of the species (i.e., a species uninomen) under this code. In this context, the species uninomen may be combined with the names of clades other than the prenomen (see Rec. 21A)."
Recommendation 21A: "When species names are used in the context of this code, it will often be useful to associate them with one or more prenomina as well as the names of more inclusive clades. Hierarchical relationships among the taxa designated by those names can be indicated in a variety of ways, but the taxa should be listed in order of decreasing inclusiveness from left to right. In addition, symbols such as those in the examples under Rec. 21.4A may be used not only with prenomina but also with names associated with groups above and below the rank of genus under the rank-based codes (but for simplicity, such symbols are not included in the following examples).
Example 1. The species originally named Anolis auratus Daudin 1802 has been placed in at least two different genera, named Anolis and Norops. If those names were to be established under this code as the names of (nested) clades, the name and relationships of the species could be indicated in any of the following ways (not an exhaustive list): Anolis/auratus Daudin 1802, or Norops: auratus Daudin 1802, or Anolis/Norops/auratus Daudin 1802, or Anolis Norops auratus Daudin 1802. For optional use of parentheses to indicate that a specific name or epithet was originally combined with a different generic name, see Note 21A.2.
Example 2. If the name of a species under the ICZN is Diaulula sandiegensis (Cooper 1863), and if Diaulula has not been established as a clade name under this code (for example, because there is presently insufficient data to establish monophyly), and if the name Discodorididae has been established as the name of a more inclusive clade under this code, then the name and relationships of the species could be indicated in any of the following ways (not an exhaustive list): Diaulula sandiegensis Cooper 1863, or Discodorididae Diaulula sandiegensis Cooper 1863, or Discodorididae/sandiegensis Cooper 1863, or Discodorididae sandiegensis Cooper 1863. For optional use of parentheses to indicate that a specific name or epithet was originally combined with a different generic name, see Note 21A.2.
Note 21A.1. By combining the second part of a species binomen with the name of a clade that is not a genus under the appropriate rank-based code (see variants that do not use the name Diaulula in Rec. 21A, Example 2), it is possible to provide phylogenetic information for a species without using a generic name (BC, ICBN) or genus-group name (ICZN) that has not been established as a clade name under this code.
Note 21A.2. If a specific name (ICZN) or epithet (BC, ICBN) is associated with just one prenomen, so the combination resembles a binomen, [â¦]"
Emphasis added. (Italics are of course not emphasis in this kind of context.)
Dartian asked for references on cessation of tooth replacement. Check out...
Erickson, G. M. 1996. Toothlessness in American alligators, Alligator mississippiensis. Copeia 1996, 739-743.
I also have photos of varanids where tooth replacement had stopped - I think they come from...
Bellairs, A. d'A. 1968. Reptiles. Hutchinson University Library, London.
Folks: the lifespan what you are discussing is sub-branch of ecology called evolution of life histories. Basically, animals which cannot expect to live long (eg. have lots of predators) reproduce early and become senescent early, and the opposite. This is called the trade-off between current reproduction and future reproduction (that is, growing, preventing ageing, preventing cancer etc). The other half of life histories is trade-off between number and quality of offspring. Shortly, to have many small young like sea turtles do, or few big ones like apes do.
So, why birds live long? Because they can fly and have fewer predators than rodents. Long-living small mammals also have few predators - flying bats, burrowing mole rats and spiny echidnas .
So, lifespan of less tha 30 of Tyrannosaurus seem better than big cats (less than 20) and something like rhinos or hippos. Here perhaps the biggest danger to T-rex were other T-rex [edit note from Darren: 'less than' symbol was used in Jerzy's original text. Have changed this because it confuses the publishing platform and causes it to remove a large chunk of the text].
Some paleontologic works suggest very weird life histories of dinosaurs. One is T-rex spending all his life as juvenile and basically being fully grown for a few years before death. Seem strange and I suspect some error there. Why to reach maximum growth and perhaps optimum breeding condition only to die? Maybe dinosaurs had some truly extraordinary life histories not found in modern animals. Eg. T-rexes lived in groups and subadults spent almost all life as non-breeding helpers. Or maybe there is an error there.
The importnat thing in ageing are that: preventing ageing is easy, you just evolve your enzymes repairing cells to work better. However, when animals don't reach the maximum lifespan, mutations kick in and destroy all cellular mechanisms to repair cells at the old age. Second, every enzyme takes energy - even little energy can be potentialy used on earlier reproduction.
Great replies, thanks. Some comments on them:
David:
A possible link between number of cervical vertebrae and cancer resistance? Wow! Reference(s), please! As for a possible link between longevity and cancer resistance, naked mole-rats almost never seem to get cancer either (Buffenstein, 2005:1375). Hmm.
H. glaber has a low metabolic rate, but it's not that much lower than in similar-sized rodents (it's only about 30% lower than in mice Mus sp.). So while metabolic rate surely plays some part in explaining extreme longevity it is probably not, by itself, a sufficient explanation.
As for for the PhyloCode clarifications, thanks. Lots to digest. Only one comment for now:
Don't you think there is a risk that some evil Linnaean traditionalists will say that "The easiest and the least disruptive solution to that problem is to divorce paleontological nomenclature from neontological nomenclature entirely"?
(Btw, do you know if 'all' those proposed species concepts are somewhere handily collected online?)
Jerzy:
The point that I was trying to make with my robin example was that even (bird) species that cannot 'expect' to live long (only slightly more than 1 year, in the robin's case), and have lots of predators, and reproduce early, may still live for very long. In other words, what needs explaining is why small birds have that potential, when most small mammals don't. Which brings us to:
I don't think lack of predation is a sufficient explanation, at least not in the case of the naked mole-rat. Heterocephalus glaber is the only fossorial small mammal (the only one that we know of anyway) with such an extended lifespan. Other small burrowers, including other bathyergids, have typical - i.e., short - small-mammal lifespans. As for the echidnas having few predators; that's probably true, but that's also true, for example, of hedgehogs, porcupines, armadillos, pangolins, and skunks - and none of them are exceptionally long-lived. Besides, do flightless birds (ratites, penguins) live significantly shorter lives than flying birds? I'm not aware of any data suggesting that they do.
Data on H. glaber do not support that contention. They are, as is well known, eusocial and the majority of the individuals in a colony never breed during their lifetimes. Yet, both breeding and non-breeding individuals reach similar advanced ages. The breeding 'queen' mole-rats do not seem to suffer any reduction in lifespan, even though they are very fecund (they're still rodents, after all): for example, one captive born breeding female reared more than 900 young in her 23.5-year lifetime (Buffenstein, 2005:1373).
More generally, this whole idea that animals must 'choose' between a) somatic maintenance & a longer life, or b) allocating resources into reproductive processes & a shorter life, is not well supported by data. Or, at the very least, it is not supported by what we've learned recently by studying H. glaber. (To anyone interested in the subject of animal longevity, I recommend reading Buffenstein (2005), which has a very insightful discussion on evolutionary and mechanistic theories of aging in animals.)
For the link between cancer and number of cervical vertebrae see...
Galis, F. 1999. Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes, and cancer. Journal of Experimental Zoology (Mol Dev Evol) 285, 19-26.
Thanks, Darren. Much obliged.
So this, too, has to do with Hox genes? Is there any known part of vertebrate development that they're not somehow involved with..?
For species perhaps. For clades it's not feasible without duplicating most names.
I don't think there's such a source online, though I haven't checked; a TREE paper from 2001 which lists 23 species concepts (almost without explanation) could be accessible. The probably best source are two recent book by Philippe Lherminier (one with a coauthor, I think); at least one of them lists 146 species concepts. Unfortunately I haven't read them.
This looks like a pretty good book I'd like to grab. I never saw that Greg Paul painting before... I really like it. Looks a lot like his rear-view T-rex pair.... was this also in the book?
Dartian,
The idea of trade-off between current in future reproduction is extremely well supported by experiments, from plants to bluetits. I gues you search for ecological papers. Its the whole subbranch of evolutionary ecology, called evolution of life histories.
About naked mole-rat:
I don't know what causes their low mortality, maybe the presence of specialized soldier class. But non-breeding helpers still face a trade-off between reproduction vs longevity - simply they contribute energy not to raising their own children but siblings.
About birds:
Always good to remind, that median and average lifespans of birds don't tell much about their longevity. Birds typically have extreme mortality of chicks and first-year juveniles, followed by significantly lower mortality of breeders. So average lifespan of small passerines can be few weeks and shorter than the age of sexual mortality.
Jerzy: first, a more general comment.
Senescence and longevity are not really that well understood even in us humans, never mind in other organisms. And this is not because of lack of interest in these subjects: to the contrary, plenty of effort has been put into research in aging. Yet we still havenât discovered ways to artificially prolong our youth* and/or our potential maximum lifespan to any significant degree. Biomedical research may, of course, change this in the future. But in light of our current understanding of animal aging, it is highly premature to make sweeping claims** about this very complex biological phenomenon.
* Botox notwithstanding.
** For example, claims such as this, in comment #52:
Now, to more specific points.
That may be the case, but it still does not address the question of why some taxa have the potential to live longer than others. What has been experimentally shown is that there appears to be a correlation between certain life history characteristics and a long lifespan; that much is true. But as we all know, correlation does not imply causation. Thus, to take an example, these two statements are not the same:
âBirds and bats can fly and they live, on average, longer than similar-sized flightless mammals.â
âBecause birds and bats can fly, they live, on average, longer than similar-sized flightless mammals.â
The latter statement is a testable hypothesis. If the ability to fly in itself, via some still-unknown physiological mechanism, is the factor that increases maximal lifespan, then one could (for example) predict that: 1) flying insects will have longer lifespans than flightless insects/arthropods, 2) flightless birds will have shorter lifespans than flying birds, and 3) in captivity, in the absence of predation etc., flightless mammals will live for as long as flying vertebrates. But empirical data strongly suggest that prediction 3 does not hold true. And Iâm not aware of any data that suggest that predictions 1 or 2 are correct either. (If you know of such data, please provide references.) Therefore, ability to fly is not alone a sufficient explanation.
Not really. Ecology can only be part of the answer (and probably not even the most important part of the answer). The ultimate cause(s) of longevity and senescence are surely physiological.
Mortality is not the issue here; the issue is potential maximum longevity. (And remember that we're talking about captive populations which experience no predation, and hardly any disease, malnutrition, or other extrinsic, 'natural' causes of death either.)
But the fact is, as I said in comment #53, that both non-reproducing and reproducing naked mole-rats live equally long lives. Also, there is no indication that the reproducing females suffer any decrease in fertility as they grow older. They do not 'burn out' or anything. You said this in a previous comment:
That sounds like an endorsement of the âdisposable somaâ theory that Thomas Kirkwood proposed in the late seventies. But, as I also said earlier, recent research has shown that it does not apply to naked mole-rats, and it may not apply to many other species either. (Again, if you know of non-anecdotal evidence to the contrary, please provide some references.)
The take-home message of the case of the naked mole-rat is this: eutherian mammal physiology does make it possible to 'have the cake and eat it too', by combining longevity with high fecundity. And in spite of their weird external appearance and unusual social system, as far as we know there is no evidence that naked mole-rats are somehow radically different from other rodents or other mammals in their cell structure or physiology. Thus, it's only prudent to conclude that the question still remains why not more rodents/mammals have evolved the potential for bird-like longevity.
Yes, that was the very point I tried to make a couple of times earlier in this thread (but perhaps not clearly enough).
Don't they do half of their thermoregulation on the burrow level instead of on the body level? They've been called "mesothermic" (halfway between endo- and ecto-).
David:
I don't know about the 'half' part, but yes, they definitely get some thermoregulatory help from their surroundings. But that does not explain why no other fossorial mammals have similarly evolved extended longevity.
gah! The proximate causes are physiological. The ultimate causes presumably depend on ecology and the evolution of life-history.
Seriously? NMRs have resting metabolic rates that are less than half those of other rodents of the same body size, at least in part due to relatively low thyroid activity. While not quite ectothermic, they are pretty crappy endotherms ("incompetent endotherms" in the words of McNab). They are indeed physiologically odd mammals. This is probably not the whole reason for their longevity, but it's almost certainly part of it.
Sven:
Ah! I made a lapsus calami.
Seriously. And the basal metabolic rates of naked mole-rats are not quite that low. I take this information from Buffenstein (2005), whom I referred to earlier, and from a more recent paper (2008) by her. There she says
"[Basal metabolic rate] of naked mole-rats is 30% lower than predicted by body mass ... but this reduction in oxygen consumption with its inevitable by-product, oxidative damage, is not sufficient to fully account for the fivefold difference in extended longevity (compared to that predicted by body mass)" (p. 443).
Maybe, but as the birds show, the link between endothermy and longevity - if there is one - is far from clear. Suffice to say that even a hummingbird, with its insanely high metabolism, may live for a double-digit number of years.
References:
Buffenstein, R. 2005. The naked mole-rat: a new long-living model for human aging research. Journal of Gerontology: Biological Sciences 60A, 1369-1377.
Buffenstein, R. 2008. Negligible senescence in the longest-living rodent, the naked mole-rat: insights from a successfully aging species. Journal of Comparative Physiology B 178, 439-445.
Deleted
Banning people no longer works on the publishing platform, does anyone know how to do it? Darren
Darren Naish has resoluted how to block his opponents but he is VERY wrong if he thinks he can stop or block the truth.
Me I personally regret this man, who calls other people "intellectually bankrupt" because he is one, along with many others, who is ENORMOUSLY bankrupt.
Let him enjoy his time, unless he will scientifically leave us. History will not even mention him, as he did nothing for science called paleontology.
Peter Mihalda
What?
What?
Ah, Peter Mihalda, the eerie oponent. I see Darren forgot to block your insanity this time
He has published.
You have not.
Good riddance.
Wow, seriously? It was from Darren's publications (both in terms of papers and blog posts) that I learned the most about Eotyrannus, placodonts, the dinosaurs of England, rhychosaurs, and a wealth of other, more obscure topics. To say he contributed nothing is both incorrect and insulting.
This time round, I will let 'Peter' have his say. Good for you, Peter. You are a wonderful human being, and I have infinite respect for your opinions.
Looking at flightless vs flying birds is going to be problematic, as most are either recent adaptations to particular niches (islands, etc)- would there be enough time for the animal to reduce its lifespan? And why would it if there are no predators on the island- would that not encourage it to become more strongly K-selected? The other group are ratites- and with the exception of the kiwi (another island endemic) they're all large ground-living birds, and therefore relatively resistant to predation.
I think evolution of flight is potentially important- its not the proximal cause, but might well be one of the ultimate causes- I wonder if something similar is going on as with turtles- while most young do not reach adulthood, but those that do, would have the potential to live a very long time- flight (and armour) make you much more resistant to predation for example. As long as a 10 year old robin is reasonably fecund there'll be selection pressure to extend the potential lifespan.
/unsupported speculation which I dont' know how to test, and doesn't quite explain bats. (The combination of flight and a shift to K-selection might though).
Deleted
Darren Naish has returned to his practices. Deleting.
I do not know but he could also work in concentration camps and who does not agree with, he may kill, or torture.
I only ask whether he is not funny to himself.
WE have a great time, thanks.
Peter