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[dinosaur] Scolomastax, new neosuchian from Cretaceous of Texas + crocodile radiation

Ben Creisler

Some recent crocodylian papers:

Scolomastax sahlsteini gen. et sp. nov.,

Christopher R. Noto, Stephanie K. Drumheller, Thomas L. Adams & Alan H. Turner (2019)
An Enigmatic Small Neosuchian Crocodyliform from the Woodbine Formation of Texas.
The Anatomical Record (advance online publication)
doi: Âhttps://doi.org/10.1002/ar.24174

New discoveries at the Arlington Archosaur Site (AAS), a Cenomanian (Late Cretaceous) locality in northâcentral Texas, are filling gaps in our knowledge of midâCretaceous Appalachian ecosystems, which remain poorly characterized. The AAS is notable because it preserves a diverse crocodyliform record. As seen in other sites that preserve four or more crocodyliform taxa, the species present at the AAS exhibit different snout shapes and body sizes, indicating that this high diversity of sympatric species was likely sustainable due to niche partitioning. Here we describe Scolomastax sahlsteini gen. et sp. nov., a new species of crocodyliform from the AAS, currently known from a partial right mandibular ramus. This species differs from other crocodyliforms in possessing features associated with durophagy or omnivory, including a shortened mandible, reduced tooth count, heterodonty, a dorsally expanded surangular, and enlarged attachments for jaw adductor muscles. Our phylogenetic analysis places this new taxon within Eusuchia as a member of Paralligatoridae and sister taxon to Paralligator gradilifrons. Scolomastax sahlsteini extends the record of paralligatorids into the Late Cretaceous of North America. This discovery represents the first appearance of this clade on the poorly known landmass of Appalachia, supporting a biogeographic connection between North America and Asia in the Early Cretaceous prior to completion of the Western Interior Seaway. However, relationships among other endemic crocodyliforms and tree instability within Paralligatoridae suggest further analysis is needed to resolve phylogenetic and biogeographic relationshipsÂ



MichaÃl P. J. Nicolaà & ÂNicholas J. Matzke (2019)
Traitâbased range expansion aided in the global radiation of Crocodylidae
Global Ecology and Biogeography (advance online publication)
doi: Âhttps://doi.org/10.1111/geb.12929

Almost half of the extant species of Crocodylia (nine genera, sensu Brochu) belong to the genus Crocodylus, which originated in the Miocene. Today, this genus has a circumtropical distribution, with representatives found in Asia, Oceania, Africa and the Neotropics. However, its geographical origin and the historical events behind its rapid diversification and global radiation are still debated. Here, we inferred the evolution of a set of life traits that aid in dispersal and how they influenced the biogeography of Crocodylus.


Time period
Cretaceous to the present.

Major taxa studied

We estimated biogeographical history on a published phylogeny using probabilistic biogeography models. Next, we identified four life traits likely to promote range expansion and used a traitâbased dispersal model jointly to infer evolution of these traits and their influence on the dispersal of crocodilians. Finally, we used diversification analyses to identify shifts in diversification rates.

An Asian origin was reconstructed for Crocodylus. Despite the small size of the phylogeny, statistical model comparison reports substantially improved the model fit of traitâdependent over traitâindependent dispersal models. In individual tests, the four life traits considered (salt tolerance, large size, large clutches and habitat generalism) appear to be correlated statistically with higher dispersal probabilities. However, the traits are likely to be correlated with each other, and we hypothesize that they all reflect the gradual evolution of a rangeâexpansion phenotype in early Crocodylus that resulted in increased diversification of the clade.

Main conclusions
Increased dispersal in the genus Crocodylus was associated with the gradual evolution of a rangeâexpansion phenotype. Interestingly, the evolution of the rangeâexpansion phenotype was also associated with the diversification of the genus in a period of global crocodilian extinction, indicating that range expansion might have served as a potential driver of speciation. This suggests that the concept of âspatial sortingâ, normally applied at the population genetic level at the leading edge of an expanding population, might also act on a macroevolutionary scale.


Daniel Zoboli, Luigi Sanciu, ÂGian Luigi Pillola & Massimo Delfino (2019)
An overview of the crocodylian fossil record from Sardinia (Italy).
[Un aperÃu sur les crocodiles fossiles de Sardaigne (Italie)]
Annales de PalÃontologie (advance online publication)
doi: https://doi.org/10.1016/j.annpal.2019.05.001

In the present contribution we focus on an overview of the Cenozoic crocodylians of Sardinia (Italy). Crocodylians from this Italian island have been published since the second half of the 19th Century and a number of papers reported on the presence of these vertebrates in 16 different localities. The remains, some of which apparently lost, are mainly represented by isolated teeth housed in historical collections of different museums (in Italy and The Netherlands) that in most cases have never been figured or described. We illustrate for the first time and provide brief descriptions of all crocodylian teeth collected in the island as well as of the still available holotype of Tomistoma calaritanum, the only crocodylian taxon established on material from Sardinia. In addition, we report crocodylian remains from two new localities, one of which testifies the presence of these vertebrates already in the Eocene record of the island.

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