‘Taeniodonta’ is polyphyletic, part 3: Conoryctes

The traditional eutherian clade
Taeniodonta‘ is polyphyletic in the large reptile tree (LRT, 1365 taxa, subset Fig. 4). Earlier here and here are parts 1 and 2 of this series.

Figure 1. Conoryctes fossil and drawing from Schoch 1986.

Figure 1. Conoryctes fossil and drawing from Schoch 1986.

Conoryctes comma (originally Hexadon molestus, Cope 1881; Schoch 1986; Paleocene; AMNH 3395). Here the Schoch drawings were not a great match for the fossil data. This taxon nests with the much earlier, Early Cretaceous marsupial, Vincelestes (Fig. 4). These were derived from Huerfanodon (Fig. 5). Note the elevated premaxila, flattened molars and deep dentary. The Schoch 1986 diagnosis of this genus is based on dental traits. He also compared Conoryctes to Huerfanodon, a related taxon in the LRT, but he also compared them to Onychonycteris, an unrelated, but convergent eutherian close to phenacodontids (Fig. 3), which is close to Conoryctella (Fig. 6) another putative taeniodont.

Figure 3. Subset of the LRT labeling several traditional taeniodonts in red, indicating the traditional clade Taeniodonta is polyphyletic and should therefore be abandoned.

Figure 3. Subset of the LRT labeling several traditional taeniodonts in red, indicating the traditional clade Taeniodonta is polyphyletic and should therefore be abandoned.

Conoryctes is so unpopular,
it has no Wikipedia entry.

Figure 4. Vincelestes soul showing the separation of the nasals and frontals by the conjoined maxillae housing giant canine roots, as in sister Thylacosmilus.

Figure 4. Vincelestes soul showing the separation of the nasals and frontals by the conjoined maxillae housing giant canine roots, as in sister Thylacosmilus.

Vincelestes neuquenianus (Bonaparte 1986, Early Cretaceous, 130 mya). Derived from a sister to HuerfanodonVincelestes is a carnivorous marsupial sister to the traditional taeniodont, Conoryctes. Note the hyper-enlarged canines and short rostrum. Premolars were not carnassial in shape, but still able to process by cutting and grinding. Nine individuals are known. Skeleton is probably a chimaera of several specimens and the degree of completion is unknown. The tail is extraordinarily long and provided with deep chevrons. Image from Digimorph.org and used with permission. Scale bar = 1 cm.

Figure 5. Heurfanodon skull. This late survivor of a Jurassic radiation is from the Eocene. It is transitional between didelphids and the Vincelestes-Thylacosmilus clade.

Figure 5. Heurfanodon skull. This late survivor of a Jurassic radiation is from the Eocene. It is transitional between didelphids and the Vincelestes-Thylacosmilus clade.

Huerfanodon torrejonius (Cope 1882; Eocene; AMNH 3224, Schoch 1986, USNM 15412) was traditionally considered a taeniodont, but here nests basal to the VincelestesThylacosmilus clade. Despite its late appearance, this taxon is more primitive than the others, which puts its genesis deep into the Jurassic. In dorsal view the skull is not compressed anterior to the jugals, similar to the ancestral Chironectes.

Figure 6. Conoryctella pattersoni nests with the Eutherian herbivore Onychonycteris in the LRT, not with the marsupial Conoryctes.

Figure 6. Conoryctella pattersoni nests with the Eutherian herbivore Onychonycteris in the LRT, not with the marsupial Conoryctes, according to the LRT, based on the present data.

References
Cope ED 1881. On some Mammalia of the lowest Eocene beds of New Mexico. Palaeontological Bulletin 33:484-495.
Schoch RM 1986. Systematics, functional morphology and macroevolution of the extinct mammalian order Taeniodonta. Bulletin of the Peabody Museum of Natural History, Yale University, New Haven. 307pp.

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