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Eucnemesaurus entaxonis
Taxonomy
Eucnemesaurus entaxonis was named by McPhee et al. (2015). Its type specimen is BP/1/6234, a set of postcrania (Posteriormost dorsal vertebrae, sacrum, anterior caudal vertebrae, pelvis and hindlimb), and it is a 3D body fossil. Its type locality is Cannon Rock Farm, Aliwal North, which is in a Norian/Rhaetian floodplain mudstone in the Elliot Formation of South Africa.
Synonymy list
| Year | Name and author |
|---|---|
| 2015 | Eucnemesaurus entaxonis McPhee et al. |
| 2016 | Eucnemesaurus entaxonis Peyre de Fabrègues and Allain p. 18 |
| 2021 | Eucnemesaurus entaxoni Müller and Garcia p. 4 |
| 2023 | Eucnemesaurus entaxonis Sciscio et al. p. 3 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Eucnemesaurus entaxonis McPhee et al. 2015
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| B. W. McPhee et al. 2015 | Two potential autapomorphies diagnose E. entaxonis: a deep brevis fossa with relatively thin lateral and medial walls on the ventral surface of the postacetabular process of the ilium (a pronounced brevis fossa is also present in the holotype of Riojasaurus, but this can be distinguished from E. entaxonis with respect to its expansive mediolateral width and considerably thicker medial and lateral margins); and a sharp ventral keel on the centra of the proximal caudal vertebrae (although this region is poorly preserved).
In addition to these features, E. entaxonis can be further diagnosed with respect to a unique suite of local autapomorphies (given its current position within our phylogeny): a small, circular pit (‘non-articulating gap’) that excavates the sacral rib of the first primordial sacral at midheight (present also in Melanorosaurus); femoral shaft beneath the fourth trochanter transversely elliptical in cross-section (present in taxa from Melanorosaurus crownwards); posterior descending process of the distal tibia does not extend as far laterally as the anterior ascending process, rendering the latter visible in posterior view (present in Aardonyx crownwards; convergently acquired in Anchisaurus); and a semi-stout pes in which the maximum proximal breadth of the first metatarsal is approximately 0.6 times its proximodistal length (present in several derived basal sauropodiform taxa). E. entaxonis differs from E. fortis in the following features: (1) E. fortis presents a femur that is subcircular in cross-section rather than elliptical, and (2) the holotype of E. fortis (TM 119) displays a distal tibia in which the mediolaterally extensive posterior surface extends as far laterally as the anterior ascending process (for articulation with the astragalus). It is possible that the distal embayment present on the fourth trochanter in E. fortis is absent in E. entaxonis, but poor preservation in the latter taxon precludes confirmation of this. Furthermore, a dorsal neural arch of E. fortis possesses a unique accessory lamina within the centrodiapophyseal fossa—a feature that cannot be confirmed in the preserved material of E. entaxonis. This feature therefore remains a valid diagnostic character of E. fortis for the time being. |