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| Pleurochayah appalachius Adrian, Smith, Noto & Grossman, 2021 |
Abstract
Four turtle taxa are previously documented from the Cenomanian Arlington Archosaur Site (AAS) of the Lewisville Formation (Woodbine Group) in Texas. Herein, we describe a new side-necked turtle (Pleurodira), Pleurochayah appalachius gen. et sp. nov., which is a basal member of the Bothremydidae. Pleurochayah appalachius gen. et sp. nov. shares synapomorphic characters with other bothremydids, including shared traits with Kurmademydini and Cearachelyini, but has a unique combination of skull and shell traits. The new taxon is significant because it is the oldest crown pleurodiran turtle from North America and Laurasia, predating bothremynines Algorachelus peregrinus and Paiutemys tibert from Europe and North America respectively. This discovery also documents the oldest evidence of dispersal of crown Pleurodira from Gondwana to Laurasia. Pleurochayah appalachius gen. et sp. nov. is compared to previously described fossil pleurodires, placed in a modified phylogenetic analysis of pelomedusoid turtles, and discussed in the context of pleurodiran distribution in the mid-Cretaceous. Its unique combination of characters demonstrates marine adaptation and dispersal capability among basal bothremydids.
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| DMNH 2013-07-1782, a partial skull and type specimen of Pleurochayah appalachius gen. et sp. nov. (a) Dorsal photograph, (b) dorsal drawing, (c) left lateral photograph, (d) left lateral drawing, (e) ventral photograph, (f) ventral drawing, (g) right lateral photograph, (h) right lateral drawing, (i) posterior photograph, and (j) posterior drawing. bo basioccipital, bs basisphenoid, cm condylus mandibularis, co condylus occipitalis, cs crista supraoccipitalis, ex exoccipital, fjp foramen jugulare posterius, fnt foramen nervi trigeminale, fp fossa pterygoidea, fpcci foramen posterius canalis caroticus internus, fr frontal, fst foramen stapediotemporale, ica incisura columella auris, iof interorbital foramen, mx maxilla, op opisthotic, or orbit, pa parietal, pal palatine, pf prefrontal, pm premaxilla, po postorbital, pr prootic, pt pterygoid, qu quadrate, so supraoccipital, sq squamosal, to tympanic opening, tb tuberculum basioccipitale, XII nervi hypoglossi. Red lines indicate visible sutures. Figure created with Adobe Creative Cloud (Adobe Inc.). |
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| Carapacial specimens of Pleurochayah appalachius gen. et sp. nov., from the Cenomanian (Upper Cretaceous) Arlington Archosaur Site (Lewisville Fm, Woodbine Gp). (a) Dorsal photograph, (b) dorsal drawing, (c) ventral photograph, and (d) ventral drawing of DMNH 2013-07-0683, neural 3. (e) Dorsal photograph, (f) dorsal drawing, (g) ventral photograph, and (h) ventral drawing of DMNH 2013-07-1998, pygal. (i) Dorsal photograph, (j) dorsal drawing, (k) ventral photograph, and (l) ventral drawing of DMNH 2013-07-0517, left costal 1. (m) Dorsal photograph, (n) dorsal drawing, (o) ventral photograph, and (p) ventral drawing of DMNH 2013-07-1999, left costal 5. (q) Dorsal photograph, (r) dorsal drawing, (s) ventral photograph, and (t) ventral drawing of DMNH 2013-07-1320, partial cf. right costal 3. (u) Dorsal photograph, (v) dorsal drawing, (w) ventral photograph, and (x) ventral drawing of DMNH 2013-07-0557, partial cf. right costal 3. (y) Dorsal photograph, (z) dorsal drawing, (aa) ventral photograph, and (ab) ventral drawing of DMNH 2013-07-1405, left costal 6. (ac) Dorsal photograph, (ad) dorsal drawing, (ae) ventral photograph, and (af) ventral drawing of DMNH 2013-07-0525, partial cf. left costal 4. (ag) Dorsal photograph, (ah) dorsal drawing, (ai) ventral photograph, and (aj) ventral drawing of DMNH 2013-07-1320, partial cf. right costal 4. (ak) Dorsal photograph, (al) dorsal drawing, (am) ventral photograph, (an) ventral drawing, (ao) posterior photograph, and (ap) posterior drawing of DMNH 2013-07-0673, right peripheral 7. (aq) Dorsal photograph, (ar) dorsal drawing, (as) ventral photograph, and (at) ventral drawing of DMNH 2013-07-1279, left peripheral 9. All parts of figure to same scale. Figure created with Adobe Creative Cloud (Adobe Inc.). |
Systematic paleontology
Pleurodira Cope, 18653
Pelomedusoides Broin, 1988
Bothremydidae Baur, 18913
Pleurochayah appalachius sp. nov.
Type locality and horizon: Cenomanian, Upper Cretaceous. Lewisville Fm, Woodbine Gp (Fig. 1). The Arlington Archosaur Site, city of Arlington, Tarrant County, Texas. Exact locality data are on file at the Perot Museum of Nature and Science, Dallas, Texas.
Etymology: “Pleuro” is Greek for “side”, with “Cha’yah” for “turtle” in the language of the Caddo, a Native American tribe that inhabited much of the Gulf Coast of North America. Species name refers to Appalachia, the region comprising eastern North America.
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| Geographical position of the type localities (red circles) of known fossil crown pleurodires in Laurasia and northern Gondwana during and prior to the Cenomanian (Upper Cretaceous). Modified from global Mollweide projection at 96.6 Ma by Scotese87. Colors of taxon text corresponds with clades at bottom left. Alb Albian, Apt–Alb Aptian/Albian, Brm Barremian, Cen Cenomanian. Figure created with Adobe Creative Cloud (Adobe Inc.). |
Conclusions
The current study places Pleurochayah appalachius gen. et sp. nov. at the base of the Bothremydidae, in an unresolved polytomy with the members of Kurmademydini (Fig. 6). It is the oldest known crown pleurodire and bothremydid from North America. This study also extends the geographic range of basal bothremydids to North America, which is significant since they were previously known only from South America prior to the Cenomanian (Fig. 9). Pleurochayah applachius gen. et sp. nov. is known from the lower middle Cenomanian, predating Algorachelus peregrinus in the uppermost middle-lowermost upper Cenomanian, and Pauitemys tibert in the uppermost Cenomanian, making it the oldest known pleurodire from North America and Laurasia. It is likely that bothremydid dispersals to North America during or prior to the Cenomanian were influenced by the vicariant event of the opening of the central Atlantic, and the periodic connection of the Western Interior Seaway to the Gulf of Mexico. However, allopatric speciation may be responsible for the multiple-continent distribution of basal bothremydids, as demonstrated for other late Early Cretaceous pelomedusoid clades. Recent discoveries of new bothremydid taxa in Central America suggest additional insight into circum-Carribbean pleurodiran migrations may be possible.
Brent Adrian, Heather F. Smith, Christopher R. Noto and Aryeh Grossman. 2021. An early Bothremydid from the Arlington Archosaur Site of Texas. Scientific Reports. 11, 9555. DOI: 10.1038/s41598-021-88905-1
New 96 million-year-old fossil represents oldest side-necked turtle in north america
