Doswelliidae

Doswelliidae Temporal range: Middle Triassic–Late Triassic PreЄ Є O S D C P T J K Pg N
Life restoration Doswellia kaltenbachi, the most well known dosweliid
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	†Proterochampsia
Family:	†Doswelliidae Weems, 1980
Genera
†Ankylosuchus †Doswellia †Jaxtasuchus †Litorosuchus? †Vancleavea

Doswelliidae is an extinct family of carnivorous archosauriforms.^[1] Doswelliids lived in North America and Europe during the Middle–Late Triassic period and were among the most derived non-archosaurian archosauriforms. The family was named by R. E. Weems in 1980 and was placed in its own suborder, Doswelliina.^[2] The Doswelliidae has long been considered a monospecific family of basal archosauriforms represented by Doswellia kaltenbachi from the Late Triassic of North America. However, a 2011 cladistic analysis during the description of Archeopelta recovered that genus as well as Tarjadia as close relatives of Doswellia, within a monophyletic Doswelliidae. Although Archeopelta and Tarjadia are now considered to be erpetosuchids unrelated to Doswellia,^[3] several other genera of archosauriforms have been classified to the family. In 2013, two additional dosweliids were named, Jaxtasuchus salomoni based on several skeletons found in the Ladinian-age Lower Keuper of Germany,^[4] and Ankylosuchus chinlegroupensis based on fragments of four vertebrae, parts of the skull and of a limb bone from the early Carnian Colorado City Formation.^[5]

Doswelliidae is defined as the most inclusive clade containing all archosauromorphs more closely related to Doswellia kaltenbachi than to Proterochampsa barrionuevoi, Erythrosuchus africanus, Caiman latirostris, (the broad-snouted caiman) or Passer domesticus (the house sparrow).^[6]

Description

Doswelliids are believed to be semiaquatic carnivores similar to crocodilians in appearance, as evidenced by their short legs and eyes and nostrils which are set high on the head. They had long bodies and tails, and their front legs were shorter than their hind legs. Unlike in some other groups of archosauriforms, doswelliids retain teeth on the pterygoid, on the roof of the mouth. Although Vancleavea had a short and deep skull, most doswelliids had slender and elongated snouts, similar to other members of Proterochampsia. Advanced doswelliids possessed dorsal ribs which splay outwards (rather than downwards), making their bodies wide and low.^[4]

Doswelliids were armored with multiple rows of bony scutes (osteoderms) on their backs. With the exception of Vancleavea, which had many different forms of smooth osteoderms, doswelliid osteoderms were characteristically covered by deep, circular pits. There is also a smooth area (an anterior articular lamina) on the front edge of each osteoderm where the preceding osteoderm overlaps. This combination of osteoderm features is also present in erpetosuchids and some aetosaurs, although the osteoderms of the latter group differ in the arrangement of the pits and the fact that the anterior articular lamina is formed by a raised bar.^[7] Doswellia had at least ten rows of osteoderms, creating a flattened carapace-like armor plate on its back. Jaxtasuchus had lighter armor, with only four rows.^[4]

Classification

The 2011 phylogenetic analysis which defined Doswellidae as a family containing multiple genera also indicated that Doswellidae was the closest large monophyletic clade to Archosauria (only the Chinese archosauriform Yonghesuchus nested closer to archosaurs).^[6] However, a phylogenetic analysis by Ezcurra (2016) recovered Doswelliidae within Proterochampsia, which was found to be the sister taxon of Archosauria. The unusual aquatic archosauriform Vancleavea was also referred to Doswelliidae in this analysis.^[7] Subsequently, Ezcurra et al. (2017) excluded Archeopelta and Tarjadia from Doswelliidae, considering them to be archosaurs of the family Erpetosuchidae instead.^[3]Litorosuchus, an aquatic archosauriform which is considered a close relative of Vancleavea, may also be a doswelliid if Vancleavea is a member of the family.

The following cladogram is after Ezcurra (2016):^[7]

References

Wikispecies has information related to Doswelliidae