fossil

Out of the Earth, Out of the Blue

milhayser — Wed, 11 Feb 2015 16:28:02 +0000

Out of the Earth, Out of the Blue

Greg Laden reports on a hominid fossil "recovered from the seabed near Taiwan" which reveals new levels of dental diversity among proto-humans and may qualify as a new species. Greg says the specimen known as Penghu "is yet another indicator that multiple different hominids lived on the Earth at the same time after the rise of Homo erectus." But why was it located underwater? In another example of what lies beneath, Dr. Dolittle marvels at "an unexpected find and very exciting moment for researchers;" the discovery of small fish and invertebrates thriving below 740 meters of ice near the coast of Antarctica. Exactly how these animals survive in the stark ecosystem has yet to be determined. Meanwhile, on Uncertain Principles, Chad Orzel reflects on the history of surprising physics discoveries. He provides as an example the discovery of the muon in 1936, a subatomic particle that no one was even looking for. Chad writes, "The eminently quotable I.I. Rabi famously responded to the news by asking 'Who ordered that?'" No one, but we'll take it.

milhayser Wed, 02/11/2015 - 11:28

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Speaking of dental history, some of my best friends and golf buddies are dentists. I’ll have to ask them some time what theories they have, if any, on how teeth evolved.

I suppose first you’d have to evolve a mouth, though I’m not sure how the creature would have sustained itself directly before and after getting the mouth. Then how the creature dealt with hard food before getting the teeth. Maybe the teeth evolved in response to the creature wishing it could chomp on harder things. But first the jaw bones would have to evolve, and have the right kind of hinges so they’d go up and down in just the right way. Then the jaws would be ready for the teeth to evolve and implant their roots in the jawbone. Then the teeth would evolve into different shapes for different purposes and position themselves in the right spots with the molars in back and the canines towards the front and whatever the others are called in the very front. People probably wouldn’t guess this if asked, but teeth are the hardest substance in your body! And each tooth is comprised of different layers - enamel, dentin, cementum, and pulp. And let’s not forget the evolution of that peculiar flesh that wraps it all up - the gums. But the teeth and mouth are no good without the all-important multipurpose tongue, the esophagus, etc.

But given that teeth can get cavities and can go haywire positionally - and so require braces or other orthodontia – maybe even an atheist would say this is evidence that teeth are not designed or at least are poorly designed and thus your God isn’t much of a God because he’s obviously not an intelligent designer. Also, I think I’ve heard about people who made the same “poorly designed” argument about the esophagus, because you use the same pipe for breathing and eating and so could choke on your food and die. I guess they never heard of the epiglottis.

Anyway, the evolution of teeth provides a lot for one to chew on.

But first the jaw bones would have to evolve, and have the right kind of hinges so they’d go up and down in just the right way. Then the jaws would be ready for the teeth to evolve and implant their roots in the jawbone.

This is reasonable speculation, and it makes sense. But it's pretty much completely backwards. There's a nice outline of the evolution of teeth in Neil Shubin's Your Inner Fish.

GregH #2:
Neil gets into teeth at about 2:40.
http://thecolbertreport.cc.com/videos/xgsf42/neil-shubin

Now I’m a believer. And for about $10 grand, I’d consider buying his book and reading it.

And the beat goes on...

dr. dolittle — Wed, 05 Nov 2014 13:40:53 +0000

And the beat goes on...

Siberian sturgeon in captivity

Drs. Thomas Eliot Haworth and Holly Shiels (University of Manchester) teamed up with Drs. Jaakko Haverinen and Matti Vornanen (University of Eastern Finland) to explore how electrical signaling in the hearts of fish have evolved by comparing Teleost fish with sturgeons. Their findings were published this month in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology.

According to the study authors, there are currently approximately 27,000 species of ray-finned fishes which make up 99% of all fishes existing today. Teleost are the most common ray-finned fishes that have adapted to life in almost any aquatic environment. Sturgeons separated from other ray-finned fishes over 300 million years ago. Although Haworth et al., refer to them as living fossils, this may not be the most accurate description of these fish. According to Dr. Daniel Rabosky (University of Michigan), "Sturgeon are thought of as a living fossil group that has undergone relatively slow rates of anatomical change over time. But that's simply not true. Our study shows that sturgeon are evolving very quickly in some ways. They have evolved a huge range of body sizes. There are dwarf sturgeon the size of a bass and several other species that are nearly as big as a Volkswagen." Regardless, an examination of how the electrical activity of hearts from sturgeons vary from teleosts is very interesting given their divergence so long ago.

The current study focused on Siberian sturgeons (Acipenser baerii), which as the name implies, can be found in major Siberian river basins. Surprisingly, the study authors found that for the most part Siberian sturgeon hearts maintained similar methods of electrical excitation as teleost fishes. However, it is unknown whether the similarity is due to their common ancestry or convergent evolution. The theory that sturgeons are indeed rapidly evolving may help explain the similarities and some of the variations between these "fossils" and teleosts. The ability to adapt to changing conditions is critical in an ever-changing environment.

Sources:
Haworth TE, Haverinen J, Shiels HA, Vornanen M. Electrical excitability of the heart in a Chondrostei fish, the Siberian sturgeon (Acipenser baerii). American Journal of Physiology - Regulatory, Integrative and Comparative Physiology. 307(9): R1157-R1166, 2014. DOI: 10.1152/ajpregu.00253.2014

Rabosky DL, Santini F, Eastman J, Smith SA, Sidlauskas B, Chang J, Alfaro ME. Rates of speciation and morphological evolution are correlated across the largest vertebrate radiation. Nature Communications 4:1958, 2013. doi:10.1038/ncomms2958

Michigan News, University of Michigan

dr. dolittle Wed, 11/05/2014 - 08:40

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Ancient bird had specialized teeth!

dr. dolittle — Tue, 08 Jan 2013 14:28:39 +0000

Ancient bird had specialized teeth!

Image Credit: Stephanie Abramowicz

Researchers have unearthed a fossil of a robin-sized bird (Sulcavis geeorum) from the Cretaceous Period in China that had teeth! This species belonged to a class of birds with teeth (Enantiornithines) that were plentiful in the age of the dinosaurs. However, the teeth of this well-preserved specimen were different. The teeth were sharp and had serrated ridges. The researchers think the ridges observed on the teeth were designed to crack open insects with hard shells, snails or perhaps even crabs. What I also found interesting about this study was the mention that modern birds still have the genes for teeth but, for whatever reason, those genes are still turned off. In fact, the report mentions that birds have lost their teeth at least 4 times according to fossil records. The traditional theory according to the author, Chiappe, is that teeth are heavy so birds evolved beaks which are lighter.

Follow Dr. Dolittle on Twitter: @DrDoScienceBlog

Sources:
O’Connor, J.K., Y. Zhang, L. M. Chiappe, Q. Meng, L. Quanguo, and L. Di. 2013. A new enantiornithine from the Yixian formation with the first recognized avian enamel specialization. Journal of Vertebrate Paleontology 33(1):1-12.

Society of Vertebrate Paleontology

dr. dolittle Tue, 01/08/2013 - 09:28

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It is not impossible that teeth genes could be switched back on again, I suppose, but the modern beak would not accomodate them well. Once the body has evolved to be toothless, it must be hard to regain them. This is surely a good example of evolutionary channeling. I was at the Holzmaden Museum in southern Germany at Christmas, where there are great fossils from the same period.

I doubt that this is also the explaination for why turtles have no teeth. ;-)

Ancient "Big Man" Confirms That Humans Stood Tall Early

laelaps — Wed, 23 Jun 2010 14:37:50 +0000

Ancient "Big Man" Confirms That Humans Stood Tall Early

The skeletons of Lucy (left) and Kadanuumuu (right). Both belong to the early human species Australopithecus afarensis. (Images not to scale.)

I never fully appreciated how small Lucy was until I saw her bones for myself. Photographs and restorations of her and her kin within the species Australopithecus afarensis had never really given me a proper sense of scale, and when I looked over her incomplete skeleton - formally known as specimen A.L. 288-1 - I was struck by her diminutive proportions. In life she would have only been about three and a half feet tall. Her physical stature seemed to be inversely proportional to the influence her bones have had on our understanding of our origins.

As it turns out, Lucy was small even compared to members of her own species. Although it is unlikely to diminish her notoriety, this week a team of paleoanthropologists led by Yohannes Haile-Selassie have released the description of another, older partial skeleton of Australopithecus afarensis discovered by Alemayehu Asfaw in the famous Afar region of Ethiopia. The discovery of this skeleton marks only the second time that parts of the forelimbs and hindlimbs of one individual A. afarensis have been found together, and it provides some new insights insights into how early humans moved.

Technically called KSD-VP-1/1, but informally dubbed Kadanuumuu (meaning "Big Man"), the newly described skeleton is represented by parts of the leg, arm, pelvis, neck, ribs, and shoulders. It is not as complete as Lucy, but there is enough of the skeleton present to know that it belonged to the same species. This specimen lived about 3.6 million years ago, almost around the same time as the A. afarensis individuals in Laetoli, Tanzania (home of the famous hominin trackway) but about 0.4 million years before Lucy. Time is not the only factor that differs between the two partial skeletons.

As the nickname suggests, "Big Man" was of a larger stature than Lucy. In general it fell within the upper range of estimates of A. afarensis body size, standing between five to five-and-a-half feet tall. Given this difference in size and characteristics of the pelvis (one of the few parts of the skeleton useful for determining the sex of an individual), the authors propose that KSD-VP-1/1 was a male, though the authors do not comment at length about sexual dimorphism between male and female members of the species.

X-rays of the scapulae of a) a modern human, b) KSD-VP-1/1, c) a gorilla, and d) chimpanzee. From Haile-Selassie et al, 2010.

Yet the most remarkable aspects of KSD-VP-1/1 relate not to size, but parts of its anatomy not seen before. Paleoanthropologists have found bits and pieces of scapulae (shoulderblades) from adult A. afarensis before, but never one as complete as in KSD-VP-1/1. When compared to the shoulderblade of our species, a gorilla, and a chimpanzee, the scientists found that the KSD-VP-1/1 scapula is "intermediate" between ours and that of a gorilla, with the chimpanzee shoulderblade being greatly different from the others (again hinting that chimpanzees have undergone a good deal of anatomical specialization in the last six million years or so and cannot be taken as perfect proxies for what our earliest hominin ancestors were like). Hence the scapulae of A. afarensis are unique - they are not quite like ours but they are quite different from those of chimpanzees - and the researchers behind the description suggest that either 1) the shoulderblades underwent significant modification once hominins started walking on the ground, or 2) that they represent a unique mode of locomotion unlike any seen among the few living hominids.

Likewise, the authors also propose that A. afarensis may have had a different thorax shape than previously thought. On the basis of the species' relative proximity to the split with the chimpanzee lineage and the ribs of Lucy, it had previously been hypothesized that A. afarensis had a funnel-shaped ribcage (narrow at the top, wide at the bottom) which helped the thorax house a big, vat-like stomach in which large amounts of plant food could be processed. The new paper disputes this hypothesis on the basis of five ribs from the upper part of the new specimen's chest. While the upper ribs of some gorillas were similar to the upper ribs of KSD-VP-1/1, overall the top ribs in the thorax were more like ours than those of living African apes. On this basis the authors state "there is clearly no evidence that the early hominid thorax was 'funnel-shaped' as previously claimed", but this is not necessarily so. The upper part of the thorax may be more like ours - or at least intermediate between ours and that of some gorillas, as was the case with the scapula - but we still do not have a clear picture of what the lower ribcage was like. Given that the references the authors cite related to this point are books and no page numbers are given it is difficult to see how their findings relate to previous research on the subject (such as the restorations made by Peter Schmid which became the basis for the funnel-ribcage restoration). At this point either ridcage hypothesis - "human-like" or "funnel-shaped" - is a hypothesis which requires future discoveries and analysis to support or reject.

In terms of arms and legs, KSD-VP-1/1 appeared to confirm to what had previously been proposed about proportions. Compared to us it would have had long arms, but compared to a chimpanzee it would have had long legs, again highlighting the disparity between the upper and lower body. Even then, the legs of A. afarensis and its relatives only appear to be moderately more elongated than those of their predecessors, and the authors take this to mean that the evolution of slightly longer legs was of limited importance to walking around on the ground.

Looking at KSD-VP-1/1 as a whole, its anatomy was well-adapted to upright walking on the ground. The transition from life in the trees to upright walking had happened long before, and while A. afarensis was still capable of climbing trees it appears to have been more at home on the ground. As stated by the authors, after the initial transition to bipedalism, which preceded A. afarensis, it seems that "highly derived terrestrial bipedality enjoyed a long period of stasis punctuated only occasionally by additional modifications to the postcranium." Notice two key words there - "stasis" and "punctuated." As we learn more about human evolution, the stop-and-go pattern of punctuated equilibrium becomes more important to understanding the branching patterns seen in our own family tree.

Haile-Selassie, Y., Latimer, B., Alene, M., Deino, A., Gibert, L., Melillo, S., Saylor, B., Scott, G., & Lovejoy, C. (2010). An early Australopithecus afarensis postcranium from Woranso-Mille, Ethiopia Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1004527107

laelaps Wed, 06/23/2010 - 10:37

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Australopithecus afarensis

Hi Brian, nice post!

I do have a few bones to pick (so to speak). You state "When compared to the shoulderblade of our species, a gorilla, and a chimpanzee, the scientists found that the KSD-VP-1/1 scapula is "intermediate" between ours and that of a gorilla," but I think this is a bit of a misreading. The authors found that there were two (largely redundant) angles in which Kadanuumuu's measurement turned out to fall in between human and gorilla measures (the angle between the glenoid and the lateral border of the scapula, and the glenoid and the bar which runs parallel to the lateral border). The PCA that the overall pattern for Kadanuumuu is more human-like.

Second, the "funnel-shaped" thorax is mainly determined not by the lower part of the rib cage, but by constriction at the top of it. The lack of constriction demonstrated by Kadanuumuu's second rib is pretty good evidence that the rib cage was not funnel-shaped.

Hey, Zinj... Nice grammar for "an early hominin described as the largest of the Paranthropus species, that lived from about 2.6 until about 1.2 million years ago during the Pliocene and Pleistocene epochs in Eastern Africa."
(I gots wikipedia and fingers!)

I read commenter "occamseraser" on The Panda's Thumb say he had his doubts about attributing the remains to afarensis due to the lack of "craniodental remains" ... What would that mean for this discovery then?

Yes, no teeth is a problem when trying to diagnose a fossil into a certain species. I'm frankly happy that they didn't just name a new species, as seems to be the trend nowadays.

It's either afarensis or anamensis, and both diagnoses would be strengthened by having teeth. I think people would complain no matter where they placed it. It's at the right place and right time to be afarensis, so I think that's probably the simplest diagnosis for now.

Zinj - Thanks for the comment. As for the "intermediate" remark, I pulled it from this sentence in the paper: "In the two redundant angles (axillaryâglenoid and barâglenoid), KSD-VP-1/1g is largely intermediate between humans and Gorilla but lies above the latterâs interquartile range." Perhaps I should have been more specific, but overall I found it interesting to see how there were some data points from gorillas which were close to KSD-VP-1/1.

Thank you, as well, for your comments about the ribcage shape. While the top ribs may not indicate such a strongly funnel-shaped thorax as proposed by Schmid, whatever reconstruction we choose is still going to be a hypothesis until we find more fossils. Likewise, I would be interested to see if ribcage shape varied between small individuals (like Lucy) and large ones like KSD-VP-1/1.

And this is not something directed only at the authors of the paper - even I have done this from time to time - but I have become frustrated by the habit of describing traits as more human-like or more ape-like based almost solely upon the anatomy of living hominids. Granted, many fossil hominins are fragmentary and may not preserve the same parts of the skeleton needed for detailed comparison, but how informative is it to say that a ~3.6 million year old hominin is more like a gorilla or more like our species when its closest relatives are not also considered? I am just thinking out loud here, but I have to wonder about how these choices for comparisons influence the way we interpret the paleobiology and relationships of these hominins.

Again, thanks for calling me out on the points you mentioned. Like anyone else I don't enjoy making mistakes or putting something down that is not entirely clear, but I learn more through the correction.

As it turns out, Lucy was small even compared to members of her own species.

Could this be interpreted as showing that Lucy was an adolescent female, not yet full-grown? And that some of the more primitive features of her anatomy are due to her juvenile physiology?

About those scapular photos...
Not being equipped to do PCA, and just going by subjective gestalt impression...
(1) In over-all shape, the chimpanzee is the outlier: much narrower.
(2) Are all four illustrated in the same orientation? Taking the center of the dense region close to the glenoid as the center of the clock-face, it looks as if the glenoid is directed toward about 10:00 o'clock in three of the photos, but more toward 11:00 in the chimpanzee photo.
(3) On the assumption that the orientations are appropriate, there is one striking feature in which KSD-VP-1/1 (easier to spell than it's other name!) resembles H. sap rather than G.g. or P.t.: the two extant African apes seem to have a strong spine directed diagonally across the face of the scapula, towards 4:00 or even 4:30, but H.s. and our hero have their only really dense "lines" closer to parallel with the top edge: 3:15 or 3:30.

Lucy was fully grown. Her long bone epiphyses are all fused/closed. She's an incredibly small female, shorter than the shortest modern human pygmies, and the "Big Man" comparison validates the consensus conclusion that this species was waaayyyyy sexually dimorphic.

Yes, anamensis is another possibility, but anamensis-afarensis is probably an evolving lineage, and the division into chronospecies is perhaps arbitrary (but a decent compromise). Au. anamensis was also a biped, so no surprises here. Dare I mention the name Kenyanthropus?? Nice comment on the NatGeo website about attribution and affinities of the "Big Man". Tim White and Co. opted not to attribute postcrania to Au. garhi even though they were found nearby precisely because there was no deinitive link to diagnostic craniodental bits.

What do you think the authors meant in reference to the scapula as having unique (but unspecified) functional affinities? Hmmmm.

How I would like if graphic restorations of extinct organsims of all sorts didn't attempt at a single result, "here, that's how it looked", but rather, or more frequently, exposed more emphatically a wider range of possibilities for their looks.

That's one heck of a sexual dimorphism (or possibly regional/niche specialisation?). Has anyone considered whether either might be pathological in some way?

Photo of the Day #947: Tyrannosaurus toe

laelaps — Tue, 22 Jun 2010 14:40:58 +0000

Photo of the Day #947: Tyrannosaurus toe

A few weeks ago I started prep work on a Tyrannosaurus rex toe bone recovered from Montana's Hell Creek Formation and kept at the New Jersey State Museum. This is how the gypsum-encrusted bone looked when I started...

... and this is how it looked at the end of last week. There's still a lot of work to do, but it is encouraging when you start seeing more bone than gypsum.

laelaps Tue, 06/22/2010 - 10:40

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new jersey state museum

cool. funny, i don't i could have told what was bone and what was quartz if i didn't already know what a t. rex toe bone looks like (thanks to a recent visit to the Los Angeles Museum. See, museums are useful!).

Looks like you could make use of a microblaster! I've prepared a bunch of fossils from CA that have quite a bit of gypsum on them; using a microblaster has yielded pretty good results so far. Man, that is A LOT of gypsum...

i know zero about the sort of work you do and whats involved,the details anyway,but i would have thought by this time someone would have come up with a "modern" way of freeing up fossils.you know,lasers,chemicals,robots--it sounds like this work is still in the 1800's,with dental picks and such..anyway..nice work,good luck with the rest.

To get through harder matrix, preparators make use of air-powered chisels, and sometimes use microblasters as I mentioned above (i.e. a sandblaster). Otherwise - chemicals are used to dissolve some types of matrix. However - just think about it. We're talking about removing rock from bone - all in all not a very complicated process. Hand tools have been used to carve stone for millenia, and clean fossils for ~200 years - they've stood the test of time.

Oh, and they're cheap, easy to use, and reliable. It's better to not overcomplicate things.

Thanks for the comments and suggestions, everyone. An air-powered chisel or similar tool would probably be a big help, but all I have to work with are dental tools, knives, and other miscellaneous things. Even though I am doing prep work the museum does not presently have a dedicated prep lab, so I am doing the best I can with what I am have got. It takes a long time, but that is probably for the best. In some places the gypsum crystals sit over more fragile areas of crumbly bone, so slow-and-steady is better when dealing with those parts! There are many more bones from this skeleton, though, so after I finish the toe bone I might invest in some tools of my own to help things along.

Brian,

That's the one issue with air scribes and microblasters - they're way more expensive than hand tools. *However*, I've seen a paper recently on a chemical that can be used to dissolve gypsum (as an application to fossil prep), which seems like it could be really useful in a lot of cases... including this. Jeeze, it looks as if that bone came from an evaporite deposit!

Small Fossil Mammals Reveal Wounds Left by the Last Great Extinction

laelaps — Wed, 16 Jun 2010 16:02:26 +0000

Small Fossil Mammals Reveal Wounds Left by the Last Great Extinction

A golden-mantled ground squirrel (Spermophilus lateralis), photographed in Bryce Canyon National Park, Utah. Though abundant at the Samwell Cave Popcorn Dome, California site during the Late Pleistocene, its numbers in the area decline at the beginning of the present Holocene epoch.

"One of the penalties of an ecological education", the naturalist Aldo Leopold once wrote, "is that one lives alone in a world of wounds." Few knew this better than he did. Despite becoming a celebrated advocate of wilderness for its own sake during the early twentieth century, Leopold began his career by hunting down large "pests" which bothered farmers - namely wolves, bears, and mountain lions. He had helped to create the very wounds he would later work to mend, but even the landscape Leopold knew had already been battered by events which took place thousands of years before.

The wolves, moose, bears, elk, big cats, and bison of the American west are impressive beasts, but they are only the remnants of a richer assemblage of large mammals which existed in North America until around 12,000 years ago. It was at that time that Saber-toothed cats, "short-faced" bears, giant ground sloths, and mammoths (among other large mammals) disappeared, part of the most recent mass extinction in earth's history. Just why these animals died out, however, is hotly debated. Rapid climate shifts, hunting by humans, hyperdisease, asteroid impact, and other hypotheses have all been forwarded in recent years, with hungry, hungry humans and the development of a warmer, wetter global climate being the prime suspects. Yet there is more to the story of the Pleistocene extinction that what became of the mammoth and mastodon. As a recent Nature paper by paleontologists Jessica Blois, Jenny McGuire, and Elizabeth Hadly points out, what happened to small mammals which scurried around the Pleistocene world can help us understand what caused the deep ecological wounds still visible today.

The trouble with solving the mystery of a mass extinction is that the fossil record only provides snapshots of what transpired. It is rare that deposits which span the duration of an extinction - from pre-extinction communities to tattered remnants - are found, but paleontologists have discovered one such place in northern California called Samwell Cave Popcorn Dome. This location not only bridges the divide between the end of the Pleistocene and the beginning of our present epoch, the Holocene, but it also contains the remains of many small mammal species which have allowed paleontologists to track the abundance of species over time.

At first glance, the species of small mammals from Samwell Cave Popcorn Dome appear to have done better than the largest of the megafauna - all of the species represented in the cave are still alive today. This does not mean that they were immune from the catastrophic events of the time. During the Pleistocene the small mammal community was relatively even, with each species represented by numerous individuals (there were few "rare" species), but at the beginning of the Holocene wider disparities opened. Suddenly some small mammal species were dominant while others became scarce. In fact, some species disappeared from the site entirely, causing a drop in diversity from 12 to 8 species (signaling local absence but not total extinction). Whereas they had been present at the site during the Pleistocene, the Mazama pocket gopher and mountain beaver were gone by the Holocene, with species like ground squirrels, chipmunks, and voles making up a smaller proportion of the community than they had previously.

The shifting abundance of small mammals occurred in two pulses, the first of which came between about 15,000 and 14,000 years ago. Some species, such as deer mice and Botta's pocket gopher, became more abundant during this time, while others, such as the Mazama pocket gopher, declined, but no species disappeared entirely. Then came another extinction pulse between 11,000 and 7,500 years ago. During this event some species were extirpated from the area while others suffered population reductions, bringing the community close to its modern-day makeup. The prolific nature of many small mammal species made them resistant to total extinction, but they were not invulnerable to drastic ecological change.

But what caused these shifts in the first place? There is no reason to suppose that these small mammals suffered from "overkill" as has been proposed for large mammals, and instead it appears that climate change was the primary culprit. As the cold, arid climate of the Pleistocene rapidly shifted to a warmer and wetter one, some species were locally wiped out, and it is not surprising that the species of pocket gophers and mountain beavers which once inhabited Samwell Cave Popcorn Dome now live in cooler areas. Furthermore, during the ecological pulses deer mice populations surged. As these mice are prolific generalists which often invaded disturbed habitats, their burgeoning numbers during the transition hints that major climate-driven ecological shifts were underway during the close of the Pleistocene. Perhaps the changes were even reinforced through the extinction of the megafauna. Apex predators and megaherbivores literally change the landscape through controlling populations of other animal species, dispersing seeds, and other activities, so perhaps the small mammal community was close to the bottom of an ecological cascade triggered by the loss of larger animals.

The modern distribution of the small mammals found around Samwell Cave Popcorn Dome is a signal of the ecological damage left by the end-Pleistocene extinction, and our species continues to pick at the wounds. Between habitat destruction and anthropogenic climate change, our species is again putting substantial pressure on these mammals and other species around the world - it is little wonder that "crisis" species which thrive is disturbed habitats, such as deer mice, are continuing to do so well. Things have not settled or slowed down. Instead it would appear that our species has picked up where the causes of the Late Pleistocene mass extinction left off, and in the fullness of geologic time the miniscule gap between the end of the Pleistocene and today may seemingly be obliterated, leaving the fossil record to tell an even more catastrophic tale of extinction.

Blois, J., McGuire, J., & Hadly, E. (2010). Small mammal diversity loss in response to late-Pleistocene climatic change Nature, 465 (7299), 771-774 DOI: 10.1038/nature09077

laelaps Wed, 06/16/2010 - 12:02

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It's worth a mention that California actually became dried during terminal Pleistocene/Holocene warming rather than wetter: http://dx.doi.org/10.1016/j.epsl.2009.10.003

When you get out to California Brian we will have to take trip up to Samwel, it is a fun cave to explore.

Pruning the Primate Family Tree

laelaps — Thu, 10 Jun 2010 18:09:44 +0000

Pruning the Primate Family Tree

"Dinah", a young female gorilla kept at the Bronx Zoo in 1914. From the Zoological Society Bulletin.

Frustrated by the failure of gorillas to thrive in captivity, in 1914 the Bronx Zoo's director William Hornaday lamented "There is not the slightest reason to hope that an adult gorilla, either male or female, ever will be seen living in a zoological park or garden." Whereas wild adult gorillas were "savage" and "implacable" beasts which could not be captured (a photo of a sculpture included in Hornaday's article depicts a gorilla strangling one man, brandishing another about with its other arm, and standing on the body of a third), young gorillas were fragile animals that did not last long in the concrete and steel enclosures made for them. One gorilla in Germany had survived for seven years, but the average lifespan of a captive juvenile gorilla was about nine months, and often considerably less than that. This was not to say that zoological parks would stop trying to capture and import young gorillas - Hornaday gave no indication that he wished to stop procuring young gorillas for his zoo - but only that visitors to the Bronx Zoo and other menageries would probably never see an adult gorilla.

Zoos had been failing miserably at keeping apes in captivity for centuries. Most of the animals captured were young individuals which had been snatched from their families or had just been orphaned by specimen collectors. They regularly died on the journey out of Africa or shortly after they arrived at their public confines. Many refused to eat, and most would become sick before passing away, but why this should be so puzzled zoologists. Perhaps, they speculated, it was a matter of climate. The cooler climates of Europe and North America were poor proxies for equatorial Africa, so it was hardly surprising that mortality was so high.

Looking back at the practices of zoos during the early 20th century, however, it is apparent that the different climates of Europe and North America cannot solely be blamed for the deaths of these apes. The traditional methods of catching and collecting wild animals which had worked for many other species caused a great deal of stress for captured apes, and the concrete and steel enclosures in which they were placed were cruel by today's standards. (Though, even under today's improved conditions, it can still be questions whether zoos are capable of keeping apes happy and healthy.) Still, in reference to climate, what is curious about the modern disparity between Africa and the places to which the young apes were shipped is that, not so very long ago, much of the northern hemisphere was inhabited by a variety of apes species. North American never had apes, but Europe and much of Asia did, making today's ape species the tattered branches of what once was a richer family tree.

Between 23 and 5.3 million years ago, during the slice of geologic time known as the Miocene, at least ten genera of hominoids (the clade representing all apes) existed at different times across Europe and Asia, and this diversity was bolstered by the presence of the closely-related pliopithecoids in the same areas. Together these types of large primates flourished in the warm, wet forests of the northern hemisphere, but by about 8.7 million years ago the hominoids and pliopithecoids were extirpated from Europe, with apes surviving only in Africa and Asia and the pliopithecoids eventually becoming entirely extinct. Several millions years before the origin of our own lineage (the hominins) in Africa, there was a major crash in Europe's primate diversity, but the key to what happened there is not found among the apes. Instead it is to be found among the herbivorous, hoofed mammals which lived on the ground below them.

The changeover among primates, and other animal groups, during the Late Miocene has been recognized for a long time. It appears that towards the close of the period seasons were becoming more intense and there was a drying trend, leading to the establishment of grasslands where there once were forests. The proliferation of grazing species during this time is in accord with this hypothesis, but the specific reactions of the fauna to these changes remains blurry. For example, high-crowned cheek teeth are characteristic of grazing animals and so it would be expected that an increased number of herbivores with high cheek teeth would indicate the spread of grasslands, but some of the animals taken as indicative of this trend only had high cheek teeth because they inherited them from their ancestors. They could have just as easily browsed on softer foods or had a more mixed diet.

Indeed, teeth can be a tricky thing. On a superficial level the overall shape of a tooth can help indicate whether an animal grazed on the plains or browsed for soft plants in forests, but extinct herbivores cannot so easily be shunted into just one category or another. Among fossil horses, especially, it has been found that some species once given the "grazer" label had more mixed diets or did not restrict their feeding to grasslands, and this enhanced resolution has often been achieved by looking at the microscopic scratch and wear patterns on teeth. Unlike bone, teeth do not heal when damaged, and so the wear caused by feeding is permanently recorded on teeth. By looking at these wear patterns paleontologists can test what was supposed on gross tooth morphology and gain a clearer indication of what an animal's ecology was like.

The scratches on the teeth of fossil herbivores from Europe provided paleontologists Gildas Merceron, Thomas Kaiser, Dimitri Kostopoulos, and Ellen Schulz with the evidence they needed to figure out the tempo of ape extinction in Europe. In a study just published in the Proceedings of the Royal Society B, the scientists looked at the short- and long-term patterns of wear on the teeth of 552 specimens of deer, bovids, "mouse deer", and "musk deer" from sites in Germany, Hungary, and Greece spanning about eleven to seven million years ago from which fossil primates had also been found. These sites record the drastic drop in primate diversity, and if changes in the diets of herbivores were recorded on their teeth, then it could signal quick alterations in habitat which drove the hominoids and pliopithecoids into extinction.

The scientists divided up their samples according to the times and places they represented and calculated the average mesowear (a measure of tooth wear over the long term judged by the height and sharpness of the cusps along the cheek-side of the upper second molar) and microwear (indicators of dietary preferences close to the organism's death based upon scratches and pits on the tooth) statistics for each. What the researchers found was that, taken together, each community of herbivores represented different habitat types in each location. The wear on the herbivore teeth differed from species to species as would be expected due to herbivores carving out their own niches while living alongside one another, and the average values calculated for each place/time period combination also represented different aspects along the scale between open grasslands and closed-in forests.

The researchers broke down the results by time period. During the Vallesian, about 11.6 to 9 million years ago, the primate Ouranopithecus occupied more open habitats shared by grazers than the other primates of Hungary and Germany, and among the latter two countries there were significantly more browsers in Germany than Hungary. These patterns changed by beginning of the next age, the Turolian, in which the similarity between the three places increased. There were more grazers in Germany and Hungary, and, oddly enough, a few more browsers in Greece, reducing the amount of disparity between the places. Grasslands spread in Germany and Hungary, while there was probably an increase in bushy shrubs in Greece.

An illustration of the habitat shifts in central Europe and Greece between 12 and 7 million years ago as determined by mesowear and microwear on fossil ruminant teeth. Wear patterns on the teeth of extant ruminants, such as the roe deer (a), were used in determining grazing or browsing preferences among fossil species. Their mesowear (b) and microwear (c) patterns were used to determine what kinds of ruminants were present in what number in each location (Greece, Germany, Hungary). The results showed that the habitats were likely more forested and exhibited more disparity during the Vallesian (squares) than during the succeeding age, the Turolian (triangles). This pattern corresponds to the drop in European primate diversity during the latter age. From Merceron et al, 2010.

The overall picture that emerged from the pool of data is that the sites in Germany, Hungary, and Greece were quickly changing in response to both global and local changes. During the span of time considered in the study, the Alps were being uplifted, there was a succession of glaciations in Antarctica, and other large-scale changes altered the global climate. These changes caused the forests of Europe to become more open and for semi-tropical type plants to become replaced by those seen at high altitudes or cooler conditions. The forests did not disappear all at once, but rather opened up and allowed the establishment of low, scrubby vegetation in the grass-dominated gaps.

Different kinds of mammals responded to these changes in different ways. While herbivorous hoofed mammals diversified as a result of the changes in low-to-the-ground vegetation, the primates lost the multi-level distribution of niches once available in the trees. This pattern is more marked in central Europe than in Greece - the authors of the paper note that the primates there did not live in a place with close tree cover, and instead their decline may be related to the increase in bushy shrubs - although the overall development of a cooler, drier climate appears to have done in primates elsewhere (such as Sivapithecus in what is now central Asia), as well.

By using the shifting diets of herbivores for proxies of climate change, the researchers were able to demonstrate that the decline in primate diversity coincided with the opening up of forests towards the end of the Miocene. The details of why these primates did not survive, especially since those in Greece lived in a more open habitat already, are not yet clear, but there appears to be a strong relationship between fluctuations in primate diversity and climate. We can see the similar changes occurring today, but among a very different group of primates being adversely affected by the activities of our species.

Lemurs are strepsirrhine primates, living members of a diverse group which split from our side of the family tree (the haplorrhines) over 55 million years ago. While their close relatives - such as lorises and galagos - range across Africa and Asia, lemurs only exist on the island of Madagascar, a place where environmental destruction has put nearly all living lemur species at risk of extinction. The chaotic nature of local politics has done nothing to help this, especially as many government officials have allowed destruction of forests to get as much money as they can before being booted from office, but the activities of people all over the world are also putting pressure on the lemurs. Much like mountain uplift and glaciations changed the climate of the Miocene, the amount of greenhouse gases our species has dumped into the atmosphere since the Industrial Revolution is also changing the climate, and according to a new paper in Global Change Biology this may have dire consequences for Madagascar's unique primates.

When the issue of human-driven climate change comes up, dwindling polar bear populations and melting glaciers most immediately come to mind. They are dramatic examples of change happening on a timescale we can see and comprehend. Despite the phrases "global warming" and "global climate change", however, it is often forgotten that fluctuations in climate affect organisms in the tropics as well as at the poles, and scientists Amy Dunham, Elizabeth Erhart, and Patricia Wright have found that for at least one species of lemur - Milne Edward's sifaka (Propithecus edwardsi) - fluctuations in climate greatly influence the survival of infant individuals past their first year.

Lemur mothers give birth to and raise their offspring according to a schedule attuned to their surroundings. The distinct divide between the wet and dry seasons means that important resources are only available during particular times of the year, and it appears that weaning schedules for lemur babies are roughly scheduled according to when fruit and soft young leaves will be the most abundant. If baby lemurs are to reach their first birthday (and beyond), timing is everything, but natural phenomena such as the El Nino Southern Oscillations may alter patterns in rainfall and other factors which are important to young lemur survival.

A graph representing Milne Edward's sifaka fecundity over time (from 1986 to 2004). The grey bars represent cyclones which made landfall in the southeastern part of the island. From Dunham et al 2010.

To figure out how climate relates to fecundity in Milne Edward's sifaka populations clustered in the southeastern part of the islands, the scientists looked at half a century's worth of climate data and two decades worth of lemur demographics to see if fluctuations in the local climate influenced lemur populations. The results confirmed what had previously been suspected on anecdotal evidence. Variations in rainfall, the regular landfall of cyclones, and alterations to local climate triggered by El Nino all influenced the mortality of infant lemurs, but each in different ways. While a drought would obviously have adverse consequences for lemurs, extreme amounts of rainfall caused by El Nino appear to be even worse as it causes the death of trees and vegetation essential to the survival of young lemurs. Cyclones are even more dramatic in their effect. A cyclone can entirely wipe out the available fruit on large trees, robbing lactating mothers of the resources they need to provide energy-rich milk for their young. The number of young which survive to their first year dip and rally according to these events, confirming that the population dynamics of this species of lemur is heavily affected by fluctuations in climate and extreme weather events.

What the results of the study suggests is that continued anthropogenic climate change may bring lemurs such as Milne Edward's sifaka closer to extinction. Natural fluctuations in climate, from the effects of El Nino to cyclones, already adversely effect the number of lemurs that are able to survive past their first year, but human-caused climate change has the potential to make the shifts in climate more extreme. Deforestation remains a significant threat to the lemurs and other parts of Madagascar's native fauna, but the development of drier dry seasons and wetter wet seasons (as has been predicted by climate models over the next century based upon the influence of human-driven climate change) may tip the scales. Even if we save Madagascar's forests, the shifts in climate may be enough to put some lemurs over the edge.

The lemurs of southern Madagascar are not the only primates in such a predicament. Habitat loss and climate change will no doubt continue to put pressure on other species all around the world, many of which are already endangered. Apes, especially, are under serious threats from our species, and should they disappear it will wipe away the vestiges of global ape diversity which existed during the Miocene. Then we would be the last ape, a lonely species left to wonder when we, too, will slip into extinction.

Merceron, G., Kaiser, T., Kostopoulos, D., & Schulz, E. (2010). Ruminant diets and the Miocene extinction of European great apes Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2010.0523

DUNHAM, A., ERHART, E., & WRIGHT, P. (2010). Global climate cycles and cyclones: consequences for rainfall patterns and lemur reproduction in southeastern Madagascar Global Change Biology DOI: 10.1111/j.1365-2486.2010.02205.x

laelaps Thu, 06/10/2010 - 14:09

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"it was hardly surprising that morality was so high"
and again "all influenced the morality of infant lemurs"!

When it came through on Google Reader, your post had an advertisement for a site promoting Intelligent Design tagged onto it. I took a screenshot, in case you want to see:

http://exploringourmatrix.blogspot.com/2010/06/sad-ads-how-creationists…

It's on a bit of a tangent from this post, but you might want to check out the book "Love at Goon Park" for another bit of history w.r.t. primates and the early 20th century view of their (and our) emotional needs.

Shadow - Thanks. Apparently I had a case of "stupid fingers" while checking through this post for typos last night.

James - Thanks for the post and link. I am not very happy with the Google ads situation, either, especially since almost any mention of "evolution" will cause an ID/creationism ad to pop up. (When Expelled was due out, it was in just about every Google ad box I saw for a few months.) It is frustrating, but then again I am glad that most of my readers (like yourself) will be more likely to laugh at such ads being attached to my posts than say "Hey, that sounds like a really good book!"

Sam - Thank you very much. I will definitely have to check it out, especially since one of my future book projects (still a few down the line) will focus on our perceptions of primates and how they have changed the way we see ourselves. Even better, the book you mentioned is by Deborah Blum, so I am sure it is a fantastic read, to boot.

Brian,

I assume that with a bit of pressure Google ads could make it possible to exclude ads based on keyword rather than just include them based on keywords. So a science blog focused on research on the species vulpes could select +Fox and -Megan, for instance... :)

Very interesting artcile, thanks. I used some of the quotes on lemurs and the El Nino effect for an Open University (UK) assignment in regard to species conservation.

Thanks again.

Pretend I can spell 'article'.

Repost: The species that domesticated itself

laelaps — Mon, 31 May 2010 08:43:05 +0000

Repost: The species that domesticated itself

The skull of Paranthropus boisei ("Zinj," "Dear Boy," "Nutcracker Man," etc.).

Louis Leakey had a problem.

During the summer of 1959 he and his wife Mary recovered the skull fragments of an early human scattered about the fossil deposits of Olduvai Gorge in Tanzania. The skull had been deposited among the shattered bones of fossil mammals and a collection stone tools, and this led Louis to conclude that it was one of our early ancestors. Only an ancestor of Homo sapiens could be a toolmaker, Louis thought, but the skull looked nothing like that of our species.

When Mary fit all the pieces of the fossil puzzle together she and Louis were greeted with a visage that was both familiar and alien. The a low-domed skull capped a face expanded sideways by massive cheek bones through which powerful muscles attached to the jaw. Overall the new skull, affectionately dubbed the "Dear Boy", was most similar to the skull of the australopithecines from South Africa, specifically a heavy-jawed type called Paranthropus that had been discovered decades before.

Louis recognized this similarity, but while he pushed Paranthropus to the sidelines of human evolution he presented the new fossil, named Zinjanthropus, as one of our ancestors. His mind was made up. The only serious barrier to this connection seemed to be a matter of time.

At the time "Zinj" was discovered the geologic timescale was still undergoing major revisions. Absolute dating techniques were still relatively new and many of the dates ascribed to human fossil sites were vastly different from what repeated testing has revealed them to be. In this case Zinj was thought to have lived within the last 600,000 years during the "Ice Age." This was not so very long ago, and it stretched credulity to think that a creature as superficially gorilla-like as Zinj had been transformed into our species during so short a time.

To settle this discrepancy Leakey appealed to the stone tools that had led him to his conclusions about Zinj. In a lecture presented to the South African Archaeological Society in 1960 Louis presented what he glibly called "Leakey's Theory", or the idea that the invention of stone tools allowed humans to domesticate themselves and accelerate evolution. Louis said;

If we are willing to concede the possibility, as I most certainly am, that the genus Homo was derived from an australopithecine resembling Zinjanthropus, then we have to ask ourselves whether or not a sufficiently long time interval elapsed between the Lower Pleistocene and the closing stages of the Middle Pleistocene to allow for the transformation, by evolution, from Zinjanthropus to something approaching Homo.

Ordinarily the answer would be "No", but Zinj was a special case. And, like other naturalists before him, Leakey appealed to domestication to provide a model by which evolution could proceed;

It is, I think, nowadays widely accepted by biologists and others, that man, by the act of domesticating animals and plants, speeds up the results of natural evolution, simply because he creates conditions more favourable to the survival and subsequent reproduction of aberrant mutants. Put in other words, the moment man creates, for any species, the new, unnatural conditions of life which we call 'domestication', he greatly accelerates the speed of the natural evolutionary processes. This is true even before he starts carrying out selective breeding.
...
It seems to me that a time interval of some 400,000 years is more than ample for the evolution of a creature like Zinjanthropus, once he domesticated himself, into Homo ... In fact, once he had become the maker of stone tools, there is no reason at all why human evolution should not have been as rapid as that of his many subsequent domestic animals.

If this sounds a little bit fuzzy, it certainly was. For Louis domestication and artificial selection did not simply provide an illustration of how evolution might work but were mechanisms that sped up evolutionary change; how else could we wind up with so many dog breeds so fast? It was not a well-reasoned argument, but it did not necessarily have to be. Everyone knew that only humans made and used stone tools, and therefore Zinj was a human despite failing to meet every other expectation previously held for a direct human ancestor.

At about the same time as Louis was delivering his 1960 address, however, his son Jonathan was finding bones that would undermine the vaunted position promised to Zinj. There was another fossil human at Olduvai, one that was more anatomically similar to us in form than Zinj, and so Louis quickly changed his mind. Within a year Zinj was booted to an evolutionary "side branch" while the new fossils took pride of place in Louis' mind as our ancestors.

But Louis could not publish his revised conclusions right away. His impetuous nature was well-known and to change positions so quickly could be hazardous. He had already academically embarrassed himself twice by claiming to find human ancestors that were nothing more than recent burials (to say nothing of the unpleasantness of his leaving his first wife with child to elope with Mary), so he waited for more extensive fossil evidence to back up his hypothesis.

Even so, Louis was itching to describe the new fossils, and by 1963 he was growing impatient. At least one of the co-authors of the paper describing the new human, Philip Tobias, thought the new fossils might represent an australopithecine and not a member of our own genus, but by 1964 Tobias relented. Together Leakey, Tobias, and John Napier announced the oldest recognized member of our own genus, Homo habilis, the crafty human who had created the stone tools and may have even murdered poor old Zinj. (Zinj would later be placed as a species of robust australopithecine, Paranthropus boisei, which lived between ~2.6 to 1.2 million years ago.)

While certainly able in the field, Louis Leakey's ambition to find the first true human ancestors often ran away with him. It seems that in Louis' view he and his team discovered our ancestors while everyone else was puttering about with evolutionary dead-ends. Once he had in mind that something was an ancestor, such as Zinj, he forcefully made the case that it was so, even if he had to abandon the very notion he had just popularized. Nor are such maneuvers entirely things of the past; paleoanthropology is still fraught with strong personalities that are constantly bickering over who has discovered our true ancestors.

laelaps Mon, 05/31/2010 - 04:43

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"To settle this discrepancy Leakey appealed to the stone tools that had led him to his conclusions about Zinj. In a lecture presented to the South African Archaeological Society in 1960 Louis presented what he glibly called "Leakey's Theory", or the idea that the invention of stone tools allowed humans to domesticate themselves and accelerate evolution. Louis said;"

I do not see here

Yeah.I dont see here.

Fossil dog lived alongside "Lucy's baby"

laelaps — Thu, 27 May 2010 09:00:10 +0000

Fossil dog lived alongside "Lucy's baby"

The skull of Nyctereutes lockwoodi as seen from the side and above. From Geraads et al, 2010.

In 2006 paleoanthropologists working in Ethiopia made a spectacular announcement - they had found the well-preserved remains of a juvenile Australopithecus afarensis, one of our prehistoric hominin relatives. Quickly dubbed "Lucy's baby" this 3.4 million year old specimen graced the cover of Nature and numerous news reports, yet its description represents only a fraction of the paleontological work being done in the area. Many other fossil animals have been found along the banks of the Awash, too, and in the latest issue of the Journal of Vertebrate Paleontology scientists Denis Geraads, Zeresenay Alemseged, RenÃ© Bobe, DennÃ© Reed have described a previously unknown species of dog which would have lived alongside the australopithecines.

The new canid, a relative of the living raccoon dog dubbed Nyctereutes lockwoodi in honor of paleontologist Charles Lockwood, is represented by a complete skull and a smattering of other material. As far as is presently known, it was a small dog - only about the size of a black-backed jackal - but it is the only canid species to be found at the site. Nyctereutes lockwoodi was not an apex predator. Instead it may have been more of a scavenger or an ecological opportunist, consuming a variety of foods rather than focusing solely upon meat.

Frustratingly, however, the habits and relationships of this canid are difficult to determine for certain. Despite their hypothesis that Nyctereutes lockwoodi may have been a generalist carnivore, the authors acknowledge that not enough is known about the paleoecology of the site to tell for sure. Furthermore, the authors are unsure about whether this dog belongs in a new genus - they have a hunch that it might, but they cannot find enough differences from Nyctereutes to make the distinction. Indeed, while it is interesting to hear the news about this canid, very little is known about it at present, and hopefully further discoveries will allow paleontologists to gain a clearer picture of how it lived and what it was related to.

DENIS GERAADS, ZERESENAY ALEMSEGED, RENE BOBE, and DENNE REED (2010). NYCTEREUTES LOCKWOODI, N. SP., A NEW CANID (CARNIVORA: MAMMALIA) FROM THE
MIDDLE PLIOCENE OF DIKIKA, LOWER AWASH, ETHIOPIA Journal of Verterbrate Paleontology, 30 (3), 981-987 : 10.1080/02724631003758326

laelaps Thu, 05/27/2010 - 05:00

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NYCTEREUTES LOCKWOODI

The DOI appears to be incorrect, or possibly just not live yet.

When you say this creature "lived alongside" the baby Australopithecus, you mean that it merely lived at the same time and in the same place, right? Not that it was domesticated?
Because the latter would be mind-shatteringly incredible.

Yes, but could it fetch Lucy's slippers?

What happened to his pet sabertooth ? How come no trace of it has been found ? That's really strange.

Fish was fossil frog's last meal

laelaps — Wed, 26 May 2010 09:00:16 +0000

Fish was fossil frog's last meal

The skeleton of Palaeobatrachus from Lake Enspel, Germany. From Wuttke and Poschmann, 2010.

In On the Origin of Species, Charles Darwin said of the fossil record:

For my part, following out Lyell's metaphor, I look at the natural geological record, as a history of the world imperfectly kept, and written in a changing dialect; of this history we possess the last volume alone, relating only to two or three countries. Of this volume, only here and there a short chapter has been preserved; and of each page, only here and there a few lines. Each word of the slowly-changing language, in which the history is supposed to be written, being more or less different in the interrupted succession of chapters, may represent the apparently abruptly changed forms of life, entombed in our consecutive, but widely separated formations.

The relatively few pages which naturalists had to work with by the time of Darwin's 1859 writing had been cobbled together from numerous discoveries in many places, and even today paleontologists must often sift through scraps as they update and revise the story of life on earth. Nevertheless, there are a few places in which a greater number of fossil "words" and "sentences" have been kept safe - sites of exceptional preservation which record tales of ancient life in exquisite detail. One such place is Germany's Lake Enspel, and in the 24 million year old vestiges of the ancient lake paleontologists have found clues to an ancient interaction between predator and prey.

As described by paleontologists Michael Wuttke and Markus Poschmann in Palaeobiodiversity and Palaeoenvironments, 24 million years ago the Lake Enspel was a body of water which had formed inside the caldera of a small volcano. This created a sort of natural trap which preserved organisms which died in the lake or slid through the forests anchored on the crater walls. Among the fossils found in the sediments from the lake bottom are skeletons of the frog Palaeobatrachus, an aquatic frog closely related to living African clawed frogs. These frogs are very rare, but one particular specimen contained a bonus.

a Close-up of the pelvic area of the frog which preserved the fish bones. b A crescent-shaped bone from the head of the fish. c Fish vertebra and bits of the fins. From Wuttke and Poschmann, 2010.

Preserved between the hips of one frog were a small accumulation of bones which, upon close inspection, turned out to belong to a fish. There were only a few bits of fin and backbone preserved in a "brown mass" representing former soft parts of the frog, but their position and preservation led Wuttke and Poschmann to suggest that the bones were from one of the frog's last meals. Since its extant relatives catch and consume fish when they can, there was little reason to think that Palaeobatrachus wasn't doing the same.

The discovery of more skeleton of frogs with fish bones preserved inside would certainly bolster this hypothesis, but the likelihood of finding such specimens is slim. The parts of lake bottom which became preserved were far from the margins of the lake where the frogs would have captured their prey, and the tangle of water plants along the edge of the ancient lake may have even acted as a filter which prevented dead frogs from drifting out further to where they could be preserved. Even so, the exquisite level of preservation at Lake Enspel records the details of a long-lost ecosystem, and finds such as the one discussed here are helping scientists flesh out the relationships of the animals which once lived within it.

Wuttke, M., & Poschmann, M. (2010). First finding of fish in the diet of a water-dwelling extinct frog Palaeobatrachus from the Upper Oligocene Fossil-LagerstÃ¤tte Enspel (Westerwald Mountains, Western Germany) Palaeobiodiversity and Palaeoenvironments, 90 (1), 59-64 DOI: 10.1007/s12549-009-0019-z

laelaps Wed, 05/26/2010 - 05:00

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