Oedaleops: why the post-cranial traits weaken the synapsid nesting

A recent paper
by Sumida et al. 2014 gives us our first look at the post-crania of Oedaleops (Fig. 1). That’s fantastic as many of Oedaleops’s sisters are also known from skulls only. Here is the abstract. Notes to follow are numbered in parentheses.

From the abstract: The Early Permian amniote Oedaleops is generally considered to be one of the basalmost pelycosaurian-grade synapsids (1). Thus it occupies a key position for understanding the phylogenetic relationships of basal synapsids (1) specifically and basal amniote interrelationships more generally. This assessment has until now been based almost exclusively on the remains of a single skull from the Lower Permian Cutler Formation of north-central New Mexico. The identification of additional cranial as well as numerous postcranial elements of at least three additional individuals now permits a more complete understanding of its anatomy and allows the first attempt at a partial body reconstruction of this basal pelycosaurian-grade synapsid. Oedaleops is confirmed as an extremely basal synapsid taxon, but the addition of postcranial data from Oedaleops to data matrices of earlier phylogenetic analyses unexpectedly weakens, as opposed to strengthens, support for the hypotheses of a monophyletic Eothyrididae (2).

(1) In the large reptile tree Oedaleops and the Caseasauria nest as derived from millerettids, far from synapsids.

(2) Adding the post-cranial traits attributed to Oedaleops cements its place within the Diadectes/Casea clade derived from Milleretta. Synapsids were not the only clade to develop a lateral temporal fenestra, as everyone knows.

Figure 1. Oedaleops with newly recovered post-crania to scale. These new traits are also derived from millerettids, not synapsids.

Figure 1. Oedaleops with newly recovered post-crania to scale. These new traits are also derived from millerettids, not synapsids. The postcrania, to know one’s surprise, is short-legged and bulky.

Langston W 1965. Oedaleops campi (Reptilia: Pelycosauria), a new genus and species from the Lower Permian of New Mexico, and the family Eothyrididae. Bulletin of the Texas Memorial Museum 9: 1–47. online pdf
Sumida SS, Pelletier V and Berman DS 2014. New information on the basal pelycosaurian-grade synapsid Oedaleops. Vertebrate Paleobiology and Paleoanthropology 2014:7-23.


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