Patagonian Mesozoic Reptiles, a book review

No time to produce anything new, so here's another recycled book review...

While the Mesozoic strata of Patagonia are particularly well known for their diverse and often spectacular dinosaurs, they have also yielded a phenomenally rich record of other Mesozoic reptiles, including turtles, squamates, plesiosaurs, ichthyosaurs, crocodilians and pterosaurs. In this multi-authored volume (another contribution to Indiana University Press's Life of the Past series), Gasparini, Salgado and Coria have edited a collection of 14 papers on the region's Mesozoic reptiles, and on their geological context and history of discovery. The volume is well illustrated and includes an excellent selection of colour plates, featuring life restorations, specimen photos and palaeogeographical maps.

Patagonia has a long and rich history of palaeontological exploration, and in the first chapter of the volume Leonardo Salgado reviews the contributions of Florentino Ameghino, Francisco Moreno, Richard Lydekker, Santiago Ross, their contemporaries and successors, and the recent contributions of José Bonaparte and colleagues. The 19th and 20th century palaeontological exploration of Patagonia went hand in hand with exploration in general, and the belief that Patagonia was a sort of savage 'lost world' inhabited by primitive people and living prehistoric beasts, including living ground sloths and plesiosaurs. This fuelled the imaginations of explorers, scientists and the general public. Luis Spalletti and Juan Franzese provide a well-illustrated and useful overview of Patagonia's palaeogeography.

An impressive list of Mesozoic testudines are known from Patagonia: they include notoemydids, chelids, podocnemidoids, meiolaniids and pancheloniids. As you might have guessed from the term pancheloniid, the author of this chapter (Marcelo de la Fuente) adopts and uses the phylogenetic nomenclature used for turtles by Joyce et al. (2004). In the following chapter, Adriana Albino reviews Patagonia's Mesozoic sphenodontians and squamates: the chapter should therefore have been titled 'Lepidosauria' but instead bears the name 'Lepidosauromorpha'. This is slightly surprising as, while the term Lepidosauromorpha is still used (e.g., Müller 2003), its content is often now very different from that originally envisioned.

Patagonia's Mesozoic lepidosaurs include a diverse assemblage of madtsoiid snakes, the controversial Dinilysia, and indeterminate iguanian and mosasaur remains. One of Patagonia's best represented fossil lepidosaurs is the particularly large Upper Cretaceous sphenodontian Kaikaifilusaurus calvoi [shown here], known from multiple skeletons from the Cenomanian Candeleros Formation. Prior to reading Albino's chapter, I hadn't realised that this is the same thing as Priosphenodon avelasi, the name that ApesteguÃa and Novas (2003) coined for this taxon in a paper that was published in Nature about a month after Kaikaifilusaurus was. Kaikaifilusaurus was based on a single lower jaw.

One of the most interesting aspects of Cretaceous palaeoecology demonstrated by Patagonian fossils is that the Mesozoic wasn't a dinosaurs-only theme park where other terrestrial animals were restricted to small body size and a furtive life in the shadows, as is so often stated. Semi-terrestrial and terrestrial crocodilians (or crocodyliforms, whichever you prefer) were diverse, and abundant, and reached large size during the Cretaceous, and it's Patagonian fossils in particular that have demonstrated this. Diego Pol and Zulma Gasparini here review Patagonia's metriorhynchids, notosuchians, sebecosuchians and peirosaurids. Some of these animals were morphologically bizarre, with dental and cranial specialisations demonstrating diverse lifestyles including herbivory [National Geographic's reconstriction of the metriorhynchid Dakosaurus andiniensis shown here].

The pterosaurs

Pterosaurs are reviewed by Laura Codorniú and Zulma Gasparini: the Patagonian pterosaur record is not exceptionally diverse - and indeed some groups are only represented by indeterminate fragments - but the incredible Loma del Pterodaustro quarry has more than made up for this by revealing a wealth of palaeobiological data on the multi-toothed filter-feeding ctenochasmatoid Pterodaustro. Puntanipterus globosus, supposedly diagnosed by detailed features of its tibiotarsus, is argued here to be synonymous with Pterodaustro as relatively uncrushed tibiotarsi of Pterodaustro are essentially identical to the Puntanipterus holotype. New comments are provided on tiny Herbstosaurus: the authors are sceptical of Unwin's (1995, 2003) proposal that this taxon is a dsungaripteroid. Unfortunate errors over measurements mean that MOZ 3625P, an indeterminate subadult pterodactyloid from the Vaca Muerta Formation, is said to have a wingspan of either 109.74 mm or 105.75 mm [sic, p. 154], depending on how the wingspan is estimated. This would make MOZ 3625P the tiniest pterodactyloid currently recognised, but, alas, the scale bar in Codorniú and Gasparini's Fig. 6.8, and their description later on the same page of a 1.10 m wingspan in the same specimen, demonstrates that these are typos. An ornithocheiroid fragment and various indeterminate pterodactyloid remains are also described; most tantalizing is their frustratingly brief mention of an azhdarchid ulna from the Turonian-Coniacian Portezuelo Formation. One recent discovery that the authors weren't able to include in their review is that of an apparently basal pterosaur in the Candeleros Formation at the famous 'La Buitrera' locality (Apesteguia et al. 2007). If this identification is correct it shows, contrary to all expectations, that 'rhamphorhynchoid' pterosaurs persisted until the Upper Cretaceous.

Dinosaurs dinosaurs dinosaurs

Ornithischian dinosaurs are reviewed by Rodolfo Coria and Andrea Cambiaso. Patagonia's ornithischian diversity is not on par with that of its saurischians: there are a few thyreophoran fragments, a partial maxilla from a heterodontosaurid, and about six ornithopods. Also worthy of note is controversial Notoceratops bonarelli, originally described as a ceratopsian but noted here to probably not be. The only known specimen is now lost, which never helps (in his chapter on the history of research in Patagonia, Salgado notes that Augusto Tapia originally found more pieces of the Notoceratops skeleton, but failed to collect them). Why Patagonian ornithischians are low in diversity compared to those of Laurasian strata is an interesting question. Does it reflect biogeographical control, or occupation of the relevant ecological niches by members of other clades? Coria and Cambiaso suggest that it doesn't and merely reflects biases in the fossil record, although they do not elaborate on this cryptic suggestion when I really think they should have. A single cervical vertebra from the La Amarga Formation was identified by Bonaparte (1996) as stegosaurian: Coria and Cambiaso note that the similarity between the specimen and definite stegosaur vertebrae is indeed striking, but the La Amarga specimen differs from indisputable specimens in having a far narrower neural canal, which makes me nervous about the identification. The Laguna Colorado Formation heterodontosaurid is referred here to Heterodontosaurus, making this one of few ornithischian genera reliably reported from more than one continent.

The Mesozoic strata of Patagonia are particularly well known for their sauropodomorphs, and yes I do mean sauropodomorphs and not sauropods because - in addition to Jurassic cetiosaur-grade taxa and Cretaceous titanosaurs - Patagonia has also yielded the plateosaur Mussaurus. In their review, Leonardo Salgado and José Bonaparte briefly survey Patagonia's sauropodomorphs: much of this feels familiar in view of Salgado and Coria (2005) and Coria & Salgado (2005). And, oh no, not another taxonomic name for a titanosaur clade: the new name Saltasaurini is coined here for 'the less [sic] inclusive clade containing Saltasaurus loricatus and Neuquensaurus australis' (p. 213). Given that titanosaur cladograms currently vary from one study to the next, I do not feel that the coining of new clade names is proving useful [the remarkable Patagonian diplodocoid Amargasaurus is shown above; image from wikipedia].

Somewhat odd is Salgado and Bonaparte's quoting of Bonaparte's 1999 statement (here translated into English) in which Bonaparte proposed that dicraeosaurids might 'correspond to the level of Patagosaurus or an even more primitive one'. It was the small size, reduced pneumaticity compared to other neosauropods and a relatively low number of cervical vertebrae that led Bonaparte to this singular conclusion: as Salgado and Bonaparte state here, this view has not been supported in any recent studies (all of which have found dicraeosaurids to be the sister-taxon to Diplodocidae), but their discussion of Bonaparte's proposal as a 'last word' on this group implies that it deserves merit. It probably doesn't.

Rodolfo Coria reviews non-avian theropods. As with some of the others chapters in the volume, there is little new here if you're familiar with the primary literature. Patagonian theropods include some of the most exciting of recently described dinosaurs: the fantastic abelisaurs Carnotaurus, Aucasaurus and Velocisaurus, the immense carcharodontosaurids Giganotosaurus and Tyrannotitan [shown here], the long-skulled unenlagiine maniraptorans, the alvarezsaurids Alvarezsaurus and Patagonykus, and others. But Coria's chapter is confused by statements that are both contradictory and incorrect, and in my opinion make this the most problematical contribution in the book.

In discussing the maniraptorans Neuquenraptor, Unenlagia comahuensis and U. paynemili, Coria first notes that the close association of three similar, closely related taxa within the same unit (the Portezuelo Formation) is surprising and indicative of high diversity. I remain perplexed why some palaeontologists often state that the presence of more than two similar contemporaneous species is at all unusual given that several or many close relatives are usually contemporaneous in modern faunas. Coria also implies, however, that Neuquenraptor and Unenlagia might be synonymous, and furthermore argues that 'there is no support to distinguish between' U. comahuensis and U. paynemili (p. 252). Elsewhere in the text however, Coria argues that U. paynemili was not convincingly shown by its describers (Calvo et al. 2004) to be referable to Unenlagia, and he notes that these authors also suggested that U. paynemili might represent a distinct genus. The section ends with the assertion that U. paynemili should be regarded as a nomen vanum, by which I assume that Coria means that the taxon should be regarded as a nomen dubium. By now you might be confused as to what Coria really makes of this taxon... or taxa, and I know I am.

While phylogenetic analyses have found pretty good support for the placement of unenlagiines within Dromaeosauridae, Coria suggests that the resemblances between the South American and Laurasian taxa might actually be due to convergence. It's fine to speculate about such a possibility I suppose, but it should always be made clear that convergence shouldn't be invoked simply because it might have occurred, but rather only when character analysis finds it to be the best conclusion based on the data. Some rather unique spellings are used for taxonomic names in this chapter, my favourite being Deynokeirus [sic] for Deinocheirus, and a skeletal reconstruction of Unenlagia comahuensis is not credited to its creator, Jaime Headden [that image is shown here].

Finally among dinosaurs, the birds are briefly reviewed by Luis Chiappe. Patagonia's Mesozoic birds include the enantiornithine Neuquenornis, the stem-ornithuromorphans Patagopteryx and Limenavis, and the diver Neogaeornis. Less well known is a possible galliform from the Portezuelo Formation (represented only by a coracoid), the second Mesozoic record of this clade.

Marine reptiles: ichthyosaurs and plesiosaurs

Ichthyosaurs have been known from Patagonia since the 1890s and good remains have been reported since the 1930s. Marta Fernández here covers the Jurassic and Cretaceous ichthyosaurs from the region, three of which were named during the 1990s (Chacaicosaurus cayi, Caypullisaurus bonapartei [shown below] and Mollesaurus periallus). Chacaicosaurus is here referred to Stenopterygius on the basis of forelimb and skull features. Caypullisaurus apparently crossed the Cretaceous-Jurassic boundary as it's present in both and Tithonian and Berriasian. Mollesaurus - argued by Maisch & Matzke (2000) to be synonymous with Ophthalmosaurus - is shown to differ from Ophthalmosaurus in many significant details, but the proportionally small sclerotic ring seen in the holotype (the key character used by McGowan & Motani (2003) to show that Maisch & Matzke had erred in their synonymisation) is argued by Fernández to be an unimportant consequence of ontogeny. That sounds unlikely given that proportional sclerotic ring size doesn't seem to change markedly during ichthyosaur ontogeny.

Stenopterygius and Ophthalmosaurus give the ichthyosaur assemblage of Patagonia a 'European' feel, but this doesn't entirely reflect my Eurocentric bias as a strong biogeographical link between Jurassic Europe and South America is inferred on the basis of other faunal similarities (having said that, pelagic taxa like Ophthalmosaurus apparently had a near-global distribution in the Jurassic). A similar comment could be made about the plesiosaurs if, that is, the identification of Liopleurodon and Pliosaurus in Patagonia is correct. Other Patagonian plesiosaurs include the Middle Jurassic Simolestes-like Maresaurus, the polycotylid Sulcusuchus, and the unusual polyodont Aristonectes. The Maastrichtian elasmosaurids Tuarangisaurus and Mauisaurus are shared, respectively, with Australia and New Zealand. Gasparini reviews all of these taxa, and provides discussion of their biogeography and distribution. The volume ends with Jorge Calvo's review of tracks, and with an overview of Mesozoic Patagonian reptiles produced by the volume's editors.

Overall it's good to see a book on Mesozoic reptiles that does more than just cover the dinosaurs, and it's nice to see the diversity of fossil turtles, squamates, crocodyliforms and marine reptiles promoted. New data and interpretations of Patagonian pterosaur, ichthyosaur and plesiosaur taxa will mean that this volume should certainly be consulted by workers who specialise on these groups, and people interested in Mesozoic faunas and fossil reptiles in general should find it useful. Weaknesses include the fact that the English is a bit shaky in some of the chapters, if not downright confusing in others, and the editing was inadequate to non-existent in places.

Zulma Gasparini, Leonardo Salgado and Rodolfo A. Coria (eds) (2007). Patagonian Mesozoic Reptiles. Indiana University Press, Bloomington and Indianapolis. 374pp. ISBN 978-0-253-34857-9, $49.95US (hardback).

This book review originally appeared in the Palaeontological Association Newsletter 62: available (for free download) here. It is reproduced with permission.

For previous Tet Zoo articles relevant to the subject of Patagonian fossil reptiles see...

• Move over Theropoda, Sebecosuchia rules
• Stupidly large snakes, the story so far

And, over at SV-POW!, check out...

• My neglected paddle-shaped dorsal neural spines, by Amargasaurus
• The controversial hypantra of Argentinosaurus
• The revenge of the controversial hypantra of Argentinosaurus
• Sauropods of 2008: Malarguesaurus

And be sure to check Tet Zoo tomorrow: BIG NEWS!

Refs - -

ApesteguÃa, S. & Novas, F. 2003. Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana. Nature 425, 609-612.

- ., Ãsi, A. & Haluza, A. 2007. New pterosaur remains from the Late Cretaceous of Argentina and an evaluation of the Late Cretaceous South American record. In HONE, D. (ed) Flugsaurier - the Wellnhofer Pterosaur Meeting. Bavarian State Collection for Palaeontology (Munich), unpaginated.

Bonaparte, J. F. 1996. Cretaceous tetrapods of Argentina. Muncher Geowissenschaften, Abhandlungen 30, 73-130.

Calvo, J. O., Porfiri, J. D. & Kellner, A. W. A. 2004. On a new maniraptoran dinosaur (Theropoda) from the Upper Cretaceous of Neuquén, Argentina. Arquivos do Museu Nacional, Rio de Janeiro 62, 549-566.

Coria, R. A. & Salgado, L. 2005. Mid-Cretaceous turnover of saurischian dinosaur communities: evidence from the Neuquén Basin. In Veiga, G. D., Spalletti, L. A., Howell, J. A. & Schwarz, E. (eds) The Neuquén Basin, Argentina: A Case Study in Sequence Stratigraphy and Basin Dynamics. Geological Society, London, Special Publications 252, 317-327.

Joyce, W. G., Parham, J. F. & Gauthier, J. A. 2004. Developing a protocol for the conversion of rank-based taxon names to phylogenetically defined clade names, as exemplified by turtles. Journal of Paleontology 78, 989-1013.

Maisch, M. W. & Matzke, A. T. 2000. The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 298, 1-159.

McGowan, C. & Motani, R. 2003. Handbook of Paleoherpetology. Part 8: Ichthyopterygia. Verlag Dr. Friedrich Pfeil, München.

Müller, J. 2003. Early loss and multiple return of the lower temporal arcade in diapsid reptiles. Naturwissenschaften 90, 473-476.

Novas, F. & Puerta, P. F. 1997. New evidence concerning avian origins from the Late Cretaceous of Patagonia. Nature 387, 390-392.

Salgado, L. & Coria, R. A. 2005. Sauropods of Patagonia: systematic update and notes on global sauropod evolution. In Tidwell, V. & Carpenter, K. (eds) Thunder-Lizards: The Sauropodomorph Dinosaurs. Indiana University Press (Bloomington & Indianapolis), pp. 430-453.

Unwin, D. M. 1995. Preliminary results of a phylogenetic analysis of the Pterosauria (Diapsida: Archosauria). In Sun, A. & Wang, Y. (eds) Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers. China Ocean Press (Beijing), pp. 69-72.

- . 2003. On the phylogeny and evolutionary history of pterosaurs. In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 139-190.