| Texasetes | |
|---|---|
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| The holotype coracoid (top) and humerus (bottom) at the USNM. | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Thyreophora |
| Clade: | †Ankylosauria |
| Family: | †Nodosauridae |
| Subfamily: | †Nodosaurinae |
| Clade: | †Panoplosaurini |
| Genus: | †Texasetes Coombs,1995 |
| Species: | †T. pleurohalio |
| Binomial name | |
| †Texasetes pleurohalio Coombs, 1995 | |
Texasetes (meaning "Texas resident") is agenus ofankylosauriandinosaurs from the lateLower Cretaceous ofNorth America. This poorly known genus has been recovered from thePaw Paw Formation (lateAlbian) nearHaslet,Tarrant County, Texas, which has also produced thenodosaurid ankylosaurPawpawsaurus.
5 miles south ofHaslet nearFort Worth,Texas, fossils of anankylosaurid were excavated from strata of the upper Albian rocks fromLower Cretaceous in thePawpaw Formation.[1] The fossils would later become theholotype (USNM 337987) ofTexasetes, consisting of a skull fragment, 2 teeth, 5cervical centra, 3sacral centra, 16caudal centra, partialscapulacoracoids, fragmentary pelvis, humeri, femora, tibiae, proximal ulnae, proximal radii, left metacarpal IV, left metatarsal IV, 3 phalanges, 2 unguals, and several osteoderms.[1][2] These remains had initially been labeled as those of asauropod, but were many years later recognized as ankylosaurian by M.K. Brett-Surman.[1] They were subsequently studied by ankylosaur expertWalter Preston Coombs, Jr, who named them in 1995 as thetype speciesTexasetes pleurohalio, the generic name meaning "Texas dweller" and the specific name meaning "sea adjacent".[1] Vickaryouset al. (2004) and Coombs (1995) describeTexasetes as having a horizontally orientedilium, an imperforateacetabulum, and "characteristically ankylosaurscapulamorphology, including a prominentacromion and prespinous fossa."[1][2][3]
Due to a lack of collection records, parts of the discovery and preservation ofTexasestes remain unknown. Strangely, the specimen preserved little dorsal armor or ribs, the fossils most commonly found in ankylosaur skeletons. This led Coombs to speculate that the individual had died on the shore or in an inland river and had been flushed out to sea, decomposing and losing many of its elements like the distal limbs.[1] The individual was then buried quickly inmarine sediments, according to the theory. This theory is the origin of the taxon's specific name meaning. Additional evidence comes in the form of paleo ecology, with nodosaurids and basal ankylosaurs being more commonly found in fluvial or marine sediments than ankylosaurids.[1][4]
Due to the fragmentary nature ofTexasetes, little is known directly from the fossils and the uncertain phylogenetic position limits inferable traits. The preserved teeth are unique in that they have a large ridge leading up to the apex of the tooth's crown, with this feature known in only one other taxon from southern England.[5] The cervical vertebrae ofTexasetes are concave, a trait shared withAnimantarx, a possibly autapomorphy for the two.Texasetes preserves a highly elongated coracoid and thick glenoid plate compared to its relativeAnimantarx.[6][1] Coombs (1995) diagnoseTexasetes as having a horizontally orientedilium, an imperforateacetabulum, and "characteristically ankylosaurscapulamorphology, including a prominentacromion and prespinous fossa."[1][3] Due to the taxon being a Nodosaurid, the taxon was covered in large armored osteoderms with smaller ossicles in-between, as inferred byPanoplosaurus, and no tail club.[7]
Coombs assigned the specimen to the familyNodosauridae,[1] but Vickaryouset al. consider itAnkylosauriaincertae sedis.[3]Pawpawsaurus may be synonymous withTexasetes due to their shared age, formation, and close phylogenetic position,[8] though lack of overlap prevents a confident answer and in Arbouret al., 2016's phylogenetic analysis however,Pawpawsaurus was found closer toEuropelta andTexasetes closer toEdmontonia. Additionally, a juvenile ankylosaur skeleton from the Paw Paw Formation was found to be closest related to neitherPawpawsaurus orTexasetes, butNiobrarasaurus in the 2016 analysis.[9] The2018 phylogenetic analysis of Rivera-Sylva and colleagues is used below, limited to the relationships withinPanoplosaurini.[10][11]
| Panoplosaurini |
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