Photos of Preserved Permian Forest

http://gizmodo.com/5887454/first-photos-of-chinas-298+million+year+old-buried-forest

Amazing Preservation of a Permian Forest Redux

Here is the abstract and link (open access) to the previously mentioned article.  It is too bad that with instantaneous preservation of a Permian ecosystem that no animals are mentioned as found. I also mistakenly stated in my previous post that the site was in China. It is actually from Mongolia.

Wang, J., Pfefferkorn, H. W., Zhang, Y., and Z. Feng. 2012.  Permian vegetational Pompeii from Inner Mongolia and its implications for landscape paleoecology and paleobiogeography of Cathaysia. PNAS, published online before print. doi: 10.1073/pnas.1115076109 


Abstract - Plant communities of the geologic past can be reconstructed with high fidelity only if they were preserved in place in an instant in time. Here we report such a flora from an early Permian (ca. 298 Ma) ash-fall tuff in Inner Mongolia, a time interval and area where such information is filling a large gap of knowledge. About 1,000 m2 of forest growing on peat could be reconstructed based on the actual location of individual plants. Tree ferns formed a lower canopy and either Cordaites, a coniferophyte, or Sigillaria, a lycopsid, were present as taller trees. Noeggerathiales, an enigmatic and extinct spore-bearing plant group of small trees, is represented by three species that have been found as nearly complete specimens and are presented in reconstructions in their plant community. Landscape heterogenity is apparent, including one site where Noeggerathiales are dominant. This peat-forming flora is also taxonomically distinct from those growing on clastic soils in the same area and during the same time interval. This Permian flora demonstrates both similarities and differences to floras of the same age in Europe and North America and confirms the distinct character of the Cathaysian floral realm. Therefore, this flora will serve as a baseline for the study of other fossil floras in East Asia and the early Permian globally that will be needed for a better understanding of paleoclimate evolution through time.

Amazing Preservation of a Permian Forest

The upcoming issue of PNAS has an article documenting amazing preservation of a Permian paleobotanical locality in China, the result of rapid burial by volcanic ash.  The actual article is not up yet but you can read about the study here.

Reassessment of the Triassic "Bee Nest" from Petrified Forest National Park

Tapanila, L., and E. M. Roberts. 2012. The earliest evidence of holometabolan insect pupation in conifer wood. PLoS ONE 7(2): e31668. doi:10.1371/journal.pone.0031668.

Background

The pre-Jurassic record of terrestrial wood borings is poorly resolved, despite body fossil evidence of insect diversification among xylophilic clades starting in the late Paleozoic. Detailed analysis of borings in petrified wood provides direct evidence of wood utilization by invertebrate animals, which typically comprises feeding behaviors.

Methodology/Principal Findings

We describe a U-shaped boring in petrified wood from the Late Triassic Chinle Formation of southern Utah that demonstrates a strong linkage between insect ontogeny and conifer wood resources. Xylokrypta durossi new ichnogenus and ichnospecies is a large excavation in wood that is backfilled with partially digested xylem, creating a secluded chamber. The tracemaker exited the chamber by way of a small vertical shaft. This sequence of behaviors is most consistent with the entrance of a larva followed by pupal quiescence and adult emergence — hallmarks of holometabolous insect ontogeny. Among the known body fossil record of Triassic insects, cupedid beetles (Coleoptera: Archostemata) are deemed the most plausible tracemakers of Xylokrypta, based on their body size and modern xylobiotic lifestyle.

Conclusions/Significance

This oldest record of pupation in fossil wood provides an alternative interpretation to borings once regarded as evidence for Triassic bees. Instead Xylokrypta suggests that early archostematan beetles were leaders in exploiting wood substrates well before modern clades of xylophages arose in the late Mesozoic.

Best Practices for Justifying Fossil Calibrations

This is a pretty substantial article from a large number of authors working in a variety of taxonomic groups regarding the proper presentation of data when looking at historical patterns in paleontology and geology. This is a must read for anyone using fossils to calibrate anything.

Parham, J. F., et al. 2012. Best practices for justifying fossil calibrations. Systematic Biology. doi: 10.1093/sysbio/syr107 [open access].

First Evidence of Late Triassic Dicynodonts from Germany

Schoch, R. R. 2012. A dicynodont mandible from the Triassic of Germany forms the first evidence of large herbivores in the Central European Carnian. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 26:119-123. DOI: http://dx.doi.org/10.1127/0077-7749/2012/0216


Abstract - A new partial mandible from the Schilfsandstein (Stuttgart Formation, Middle Carnian) of southern Germany forms the first unambiguous evidence of dicynodonts in the German Triassic. The preserved anterior part of the mandible is most consistent with kannemeyeriiform dicynodonts known from the Middle and Late Triassic of South America, southern Africa, North America, and the Eastern European Platform. Extrapolation of body size from the mandible indicates that the Schilfsandstein dicynodont was moderately large (∼2m estimated body length). This find is significant as it forms the first evidence of large herbivores in the Carnian pre-dinosaur faunas of Central Europe.         

Timing of the Earliest Known Feathered Dinosaurs

Edging a bit closer......


Liu, Y.-Q., Kuang, H.-W., Jiang, X.-J., Peng, N., Xu, H.,  and H.-Y. Sun. 2012. Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota. Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication) http://dx.doi.org/10.1016/j.palaeo.2012.01.017


Abstract - The Early Cretaceous Jehol Biota in China has produced numerous well preserved fossils of feathered theropods and early birds. Recent discoveries of feathered dinosaurs, as well as transitional pterosaurs and a sexually mature individual of Darwinopterus preserved together with an egg from the Daohugou Biota of an earlier age than the Jehol Biota, in northeastern China, have greatly enriched our knowledge of the transition from dinosaurs to birds and primitive to derived pterosaurs. The age estimate of fossils or host strata, however, has proven to be contentious and varies widely from the Middle Jurassic to the Early Cretaceous. Here, we report a SHRIMP U-Pb zircon date unambiguously associated with the fossil horizons, and thus, for the first time, provide an age calibration for the earliest appearance of feathered dinosaurs and transitional pterosaurs. Date results indicate that the feathered dinosaurs of China were present more than 161 Ma ago, unquestionably older than Archaeopteryx in Germany, and are the earliest known feathered dinosaurs in the world. Furthermore, feathers appeared in ornithischians before 159 Ma rather than late in the Early Cretaceous. The known transitional pterosaurs first emerged before 161 Ma. The Daohugou Biota, containing mammals, primitive pterosaurs, insects and plants, in addition to the feathered dinosaurs, was living in Inner Mongolia, western Liaoning and northern Hebei in northeastern China during the Middle Jurassic.

Guest Post - Roland Sookias Discusses His New Study Examining How Dinosaurs Came to Fill Most Ecological Niches During the Mesozoic

Why were dinosaurs, and other archosauromorphs (the group of animals including crocodiles, dinosaurs, pterosaurs and several other extinct groups), so big? Was natural selection for increasing size responsible for archosauromorphs’ dramatic rise to larger sizes and did selection for decreasing size drive therapsids’ (‘mammal-like reptiles’, which were the dominant land vertebrates before archosauromorphs) reduction in size during the Triassic (see picture)? These are the questions which my, Richard Butler’s and Roger Benson’s recent publication in Proceedings of the Royal Society B – “Rise of dinosaurs reveals major body size transitions are driven by passive processes of trait evolution” – attempts to answer.
Most of the work in the paper was done as part of my MSc thesis project, which Richard, Roger and Andrew Smith supervised. To carry out the project I spent a good deal of last summer collecting femur and skull length measurements (which we used as proxies for body mass) in the Natural History Museum Library, London. Though barely seeing daylight for a month or two, I managed to collect measurements for ~200 species, which, in combination with data from Benson et al. 2011 got us to >400 species in total. To answer the questions above we focused on getting data for archosauromorphs and therapsids from the Late Permian to Middle Jurassic. This allowed comparison between the two groups, and the interval brackets the rise of archosauromorphs to become the dominant terrestrial vertebrates, replacing therapsids. Thus it allowed us to look at body size evolutionary dynamics during a major faunal transition.

Archosauromorphs (dinosaurs, crocodiles, pterosaurs and their relatives) increased greatly in maximum size (black line, black triangles) from the Permian to Jurassic, and therapsids (‘mammal-like reptiles’) decreased. However in both this was due to expansion in the size variance (i.e. both size increase and decrease), but with subsequent extinction of larger therapsid species. Figure from Sookias et al. 2012, Proc Roy Soc B.

Once we’d got the data together we analysed them using maximum likelihood model fitting approaches. We tried both phylogenetic – i.e. incorporating evolutionary relationships – and time series (ignoring within-group evolutionary relationships and simply averaging size within time ‘bins’) models. Time series models confirmed that on average archosauromorphs tended to increase across the time interval, and that therapsids got smaller. However when we included phylogeny (evolutionary relationships) we found that there was no directional trend in either group along individual lineages. Thus the apparent trends through time were in fact due to ‘passive expansion’ in size, but as the original size was nearer the bottom than the top of the eventual size range the average size tended to increase (see picture). We thus can say that the long-repeated idea of “Cope’s rule” – that taxa in a clade tend to get larger over time due to within-lineage natural selection for larger body sizes – is not found in either archosauromorphs or therapsids during this time interval.

Our work excludes larger size in archosauromorphs as an explanation for their success, as if larger size was especially beneficial one would expect a directional evolutionary trend towards larger sizes. Instead, archosauromorphs probably replaced therapsids opportunistically, as many have hypothesized before. However, the exceptionally high growth, and thus reproductive, rates of archosauromorphs may have allowed them to re-fill empty ecological niches especially easily and rapidly after they went empty due to extinction of therapsids. Thus, while size and growth rate probably did not allow archosauromorphs to outcompete therapsids, it did allow them to fill up free niches quickly.

We also found that archosauromorph predators exceeded the size of the largest herbivores – anomodont therapsids – during the Middle-early Late Triassic. This finding – that the largest carnivores are larger than herbivores - is extremely rare in ecosystems throughout time. It demonstrates that extinct archosauromorphs really were exceptionally large, and that they were able to grow to larger sizes than therapsids given the same resources.

Well, there’s not much more to say about that paper except hope you enjoy it! However, we should be publishing some more work based on my MSc thesis in the near future, so stay tuned, and I’ve just started a PhD with Richard Butler on the early archosauromorph radiation, so hopefully I’ll be involved in answering a few more interesting questions in the coming years. Finally, a very big thank you to Bill Parker for giving us a guest slot here on the esteemed Chinleana.

The paper’s full citation is:


Sookias, R. B., Butler, R. J., Benson, R. B. J. (2012). Rise of dinosaurs reveals major body size transitions are driven by passive processes of trait evolution. Proceedings of the Royal Society B.
doi: 10.1098/rspb.2011.2441 



Abstract- A major macroevolutionary question concerns how long-term patterns of body-size evolution are underpinned by smaller scale processes along lineages. One outstanding long-term transition is the replacement of basal therapsids (stem-group mammals) by archosauromorphs, including dinosaurs, as the dominant large-bodied terrestrial fauna during the Triassic (approx. 252–201 million years ago). This landmark event preceded more than 150 million years of archosauromorph dominance. We analyse a new body-size dataset of more than 400 therapsid and archosauromorph species spanning the Late Permian–Middle Jurassic. Maximum-likelihood analyses indicate that Cope’s rule (an active within-lineage trend of body-size increase) is extremely rare, despite conspicuous patterns of body-size turnover, and contrary to proposals that Cope’s rule is central to vertebrate evolution. Instead, passive processes predominate in taxonomically and ecomorphologically more inclusive clades, with stasis common in less inclusive clades. Body-size limits are clade-dependent, suggesting intrinsic, biological factors are more important than the external environment. This clade-dependence is exemplified by maximum size of Middle–early Late Triassic archosauromorph predators exceeding that of contemporary herbivores, breaking a widely accepted ‘rule’ that herbivore maximum size greatly exceeds carnivore maximum size. Archosauromorph and dinosaur dominance occurred via opportunistic replacement of therapsids following extinction, but were facilitated by higher archosauromorph growth rates.



Popular press coverage:

http://news.discovery.com/animals/how-dinosaurs-got-so-big-120131.html

http://news.sciencemag.org/sciencenow/2012/01/the-secret-of-dinos-success.html?ref=hp

Largocephalosaurus, a New Eosauropterygian from the Middle Triassic of China

Cheng, L., Chen, X., Zeng, X., and Y. Cai. 2012. A new eosauropterygian (Diapsida: Sauropterygia) from the Middle Triassic of Luoping, Yunnan Province. Journal of Earth Science 23:33-40. DOI: 10.1007/s12583-012-0231-z

Abstract - A new eosauropterygian, Largocephalosaurus polycarpon gen. et sp. nov., was described based on a skeleton from the Middle Triassic of Luoping, Yunnan Province, southwestern China. The new taxon is characterized by a big skull, paired frontal, laterally expanded upper temporal fossa, anterior process of squamosal entering orbit, robust teeth with basally expanded crown and blunt tip, short cervical region, distinctly elongated transverse process of the dorsal vertebrae, short and broad dorsal ribs, stout gastralia, scapula with distinctly posterodorsally extending blade, distinctly robust humerus, eleven carpal ossifications, and a manual fomula of 2-3-4-5-5. A phylogenetic analysis suggests that Largocephalosaurus is the basal-most member of a clade including Wumengosaurus, European pachypleurosaurs, and Nothosauroidea.

Tikiguania Is Not From the Triassic

Hutchinson, M. H., Skinner, A., and M. S. Y. Lee. 2012. Tikiguania and the antiquity of squamate reptiles (lizards and snakes). Biology Online published before print. doi: 10.1098/rsbl.2011.1216

Abstract - Tikiguania estesi is widely accepted to be the earliest member of Squamata, the reptile group that includes lizards and snakes. It is based on a lower jaw from the Late Triassic of India, described as a primitive lizard related to agamids and chamaeleons. However, Tikiguania is almost indistinguishable from living agamids; a combined phylogenetic analysis of morphological and molecular data places it with draconines, a prominent component of the modern Asian herpetofauna. It is unlikely that living agamids have retained the Tikiguania morphotype unchanged for over 216 Myr; it is much more conceivable that Tikiguania is a Quaternary or Late Tertiary agamid that was preserved in sediments derived from the Triassic beds that have a broad superficial exposure. This removes the only fossil evidence for lizards in the Triassic. Studies that have employed Tikiguana for evolutionary, biogeographical and molecular dating inferences need to be reassessed.                 

New Postcranial material of Proterochampsa barrionuevoi from the Upper Triassic of Argentina

Trotteyn, M. J. 2011. Material postcraneano de Proterochampsa barrionuevoi Reig, 1959 (Diapsida: Archosauriformes) del Triásico Superior del centro-oeste de Argentina. Ameghiniana 48:424-446. 

 

Resumen - Los proterochámpsidos son miembros del clado Archosauriformes y se distinguen del resto por presentar cráneo predominantemente deprimido, transversalmente expandido en el extremo posterior, hocico angosto y alargado longitudinalmente, y narinas ubicadas sobre la línea media, ausencia de postfrontal y presencia de pie asimétrico. La familia Proterochampsidae se compone de cinco géneros presentes en las formaciones triásicas de Argentina y Brasil. En esta familia se incluye la especie argentina Proterochampsa barrionuevoi Reig, proveniente de la Formación Ischigualasto (Triásico Superior). Este taxón era conocido por el cráneo y algunas vértebras cervicales, pero el resto del material poscraneano era totalmente desconocido hasta el presente. En esta contribución se describe detalladamente un ejemplar de Proterochampsa barrionuevoi (PVSJ 606), incluyendo el cráneo, toda la serie vertebral, escápulas, coracoides, cintura pélvica, húmero derecho, radio y ulna del mismo lado, ambos fémures y miembro posterior derecho casi completo. Asimismo se presenta una diagnosis enmendada para la especie, constando de los siguientes caracteres neurocraneales diagnósticos: depresión semilunar expuesta ventrolateralmente, fosa basiesfenoidea rodeada rostrolateralmente por un reborde con forma de “V” con sus ramas convexas. Entre los caracteres que diferencian a P. barrionuevoi de la especie brasilera P. nodosa se citan: angostamiento anterior del hocico menos gradual que el de P. nodosa, occiput más deprimido, narinas lanceoladas con ambos extremos aguzados y frontal menos irregular que el de P. nodosa.

POSTCRANIAL MATERIAL OF PROTEROCHAMPSA BARRIONUEVOI REIG, 1959 (DIAPSIDA: ARCHOSAURIFORMES) FROM THE UPPER TRIASSIC OF CENTRAL-WESTERN ARGENTINA.

Abstract - Proterochampsids are members of the clade Archosauriformes, a group distinguished from others because of its depressed skulls transversely expanded at the posterior end, narrow and longitudinally long snout, nares located close to the midline, absence of postfrontals, and presence of an assymmetric pes. The family Proterochampsidae includes five genera recorded in Triassic formations of Argentina and Brazil. In this family is included the Argentinean species Proterochampsa barrionuevoi Reig, from the Late Triassic Ischigualasto Formation. This taxon was known from skulls and cervical vertebrae, but the rest of the postcranium remained unknown until now. Herein, a new and almost complete specimen of Proterochampsa barrionuevoi is described in detail (PVSJ 606). The specimen includes skull, complete vertebral series, scapulae, coracoids, pelvic girdle, right humerus, right radius and ulna, both femora, and complete right hindlimb. An emended diagnosis considering neurocranial features –semilunar depression ventrolaterally exposed, basisphenoidal fossa surround by a rostrolateraly V-shaped ridge with convex branches– is provided. The features distinguishing P. barrionuevoi from the Brazilian species P. nodosa are: snout becoming narrow anteriorly in a less gradual manner than in P. nodosa, lower occiput, nares lanceolate with narrow anterior and posterior ends, and frontal less irregular that in P. nodosa.

Oldest Known Dinosaurian Nesting Site

Here is the abstract and link to the article discussed in the linked news report from yesterday.

Reisz, R. R., Evans, D. C., Roberts, E. M., Sues, H.-D., and A. M. Yates. 2012. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus. PNAS online before print. DOI 10.1073/pnas.1109385109

Abstract - The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding.

Massospondylus Nesting Site from the Early Jurassic of South Africa

http://www.cbc.ca/news/technology/story/2012/01/23/sci-dinosaur-nesting-site.html

Aetobarbakinoides brasiliensis, a New Aetosaur from the Late Triassic of Brazil

This is an interesting new specimen from the Santa Maria Formation of Brazil. I've had the chance to personally study this material and although poorly preserved and despite possesses a radial patterning of the dorsal osteoderms it clearly does not belong to the South American genera Aetosauroides or Neoaetosauroides mainly because of characteristics of the vertebrae. In fact, the vertebrae with their well developed accessory processes and lack of ventral keels strongly resemble those of desmatosuchines. This is supported by the phylogenetic analysis.

Notably this is the first aetosaur taxon to be diagnosed using postcranial characters rather than those of the osteoderms. Indeed only a few poorly preserved osteoderms are present in the specimen. I've argued in the past that despite the long use of armor ornamentation to diagnose aetosaur species, new specimens are demonstrating that these characters are highly convergent between hypothesized main aetosaur clades and caution must be used.

This paper also finds Aetosaurinae (sensu Parker, 2007) to be paraphyletic. Again this is not surprising given the poor support for the clade in the original analysis, the fact that Aetobarbakinoides possesses "Aetosaurinae"-like armor with desmatosuchine-like vertebrae, and the fact that lateral armor is lacking in this new taxon whereas lateral armor characters strongly affect the topology of Parker (2007). This is not surprising given that the analysis of Parker (2007) was explicitly testing the phylogenetic signal of lateral osteoderms in aetosaurs.

This analysis also recovers Aetosauroides outside of Stagonolepididiae (sensu Heckert and Lucas, 2000), which demonstrates the presence of non-stagonolepidid aetosaurs. Thus the names Stagonolepididae and Aetosauria cannot be used interchangeably (as they commonly are) as I cautioned in 2007.

There is much more work today with the phylogeny of the Aetosauria and many new undescribed specimens.  I am focusing on a lot of these in my ongoing PhD work.

Desojo, J. B., Ezcurra, M. D., and E. E. Kischlat. 2012. A new aetosaur genus (Archosauria: Pseudosuchia) from the early Late Triassic of southern Brazil. Zootaxa 3166:1-33.

Abstract - We describe the new aetosaur Aetobarbakinoides brasiliensis gen. et sp. nov. from the early Late Triassic (late Carnian early Norian) Brazilian Santa Maria Formation. The holotype is composed of a partial postcranium including several cervical and dorsal vertebrae and ribs, one anterior caudal vertebra, right scapula, right humerus, right tibia, partial right pes, and anterior and mid-dorsal paramedian osteoderms. Aetobarbakinoides is differentiated from other aetosaurs by the presence of cervical vertebrae with widely laterally extended prezygapophyses, mid-cervical vertebrae with anterior articular facet width more than 1.2 times wider than the posterior one, anterior caudal vertebrae with extremely anteroposteriorly short prezygapophyses, elongated humerus and tibia in relation to the axial skeleton, and paramedian osteoderms with a weakly raised anterior bar. A cladistic analysis recovered the new species as more derived than the South American genera Aetosauroides (late Carnian-early Norian) and Neoaetosauroides (late Norian-Rhaetian), and it is nested as the sister-taxon of an unnamed clade, composed of Typothoracisinae and Desmatosuchinae, due to the absence of a ventral keel in the cervical vertebrae. Aetobarbakinoides presents a skeletal anatomy previously unknown among South American aetosaurs, with the combination of presacral vertebrae with hyposphene, anteroposteriorly short and unkeeled cervical vertebrae, gracile limbs, and paramedian osteoderms with a weakly raised anterior bar. Aetobarbakinoides is among the oldest known aetosaurs together with Aetosauroides from Argentina and Brazil and Stagonolepis robertsoni from Scotland, indicating Aetobarbakinoides, which is one of the oldest known aetosaurs, is in agreement with an older origin for the group, as it is expected by the extensive ghost lineages at the base of the main pseudosuchian clades.