New specimen of <i>Cacops woehri</i> indicates differences in the ontogenetic trajectories among cacopine dissorophids

Abstract

Abstract. The Lower Permian Dolese locality has produced numerous exquisitely preserved tetrapod fossils representing members of a lower Permian upland fauna. Therein, at least nine taxa of the clade Dissorophoidea, ranging in size from the large predaceous trematopid Acheloma to the miniaturized amphibamid Doleserpeton, highlight the great taxic and ecological diversity of this anamniote clade. Here we describe a large specimen of the dissorophid Cacops woehri, which was previously only known from the juvenile or subadult holotype skull. Another member of the genus Cacops present at the Dolese locality, Cacops morrisi, is also represented by specimens spanning juvenile, subadult, and adult stages, allowing for a comparison of morphological changes taking place in the late phases of the ontogenetic trajectory of cacopine dissorophids. The new find shows that, in contrast to C. morrisi and C. aspidephorus, C. woehri only undergoes relatively subtle changes in skull morphology in late ontogeny and retains the overall more gracile morphology into adult stages. This includes retention of the rather shallow skull shape as well as a pattern of sculpturing consisting of elongate ridges and grooves and a large occipital flange. This suggests somewhat different functional demands in C. woehri than in other known species of Cacops, possibly associated with a different ecology paralleling the great taxic diversity of dissorophoids at the Dolese locality.

Dissorophid diversity at the early Permian cave system near Richards Spur, Oklahoma, USA

“…The sutural patterns are the same as in the holotype, with the exception of a maxilla that is clearly excluded from the orbit ( Figures 6, 7). OMNH 79338 conforms well to ontogenetic changes described by Fröbisch et al (2015), such as increased size of the occipital flange, little change in the development of the ornamentation and the absence of a long ventral process of the postorbital. ROMVP 80080 and ROMVP 80081 are partial snouts, both broken just posterior to the choana (Figure 8).…”

“…The presence of dissorophids at the Richards Spur locality has been known for several decades (e.g., Bolt, 1974aBolt, , 1977Sullivan et al, 2000), but much of this material was fragmentary or isolated and difficult to fully compare with other members of the clade from coeval localities. Following intensive collection and study in the twentyfirst century, the eucacopines Cacops morrisi (Reisz et al, 2009;Gee and Reisz, 2018a) and Cacops woehri (Fröbisch and Reisz, 2012;Fröbisch et al, 2015) are now well-known, established components of the locality. A more taxonomically ambiguous skeleton was described by Gee and Reisz (2018b) and identified as a dissorophine dissorophid distinct from Dissorophus and Broiliellus.…”

Postcrania of large dissorophid temnospondyls from Richards Spur, Oklahoma

“…Cacops, and the other to the subfamily Dissorophinae. The latter specimen represents the first report of a dissorophine at the Richards Spur locality, thereby expanding the known temnospondyl diversity at the locality, as previously, the dissorophids were represented only by eucacopines Cacops morrisi and C. woehri (Reisz et al, 2009;Fröbisch and Reisz, 2012). Dissorophines, represented by several species of Broiliellus and Dissorophus multicinctus, are known almost exclusively from Texas -B. reiszi is known from New Mexico -and the first record of the clade at Richards Spur expands their biogeographic range.…”

“…For example, a comparison of the postcrania of the co-occurring C. morrisi (Gee and Reisz, 2018) and C. woehri (presently unknown) could offer some preliminary insights into the degree of variation within Cacops. The presence of two eucacopines at the Richards Spur locality with distinct cranial morphologies has led to the hypothesis that they may have been ecologically distinct to a certain degree (Fröbisch and Reisz, 2012;Fröbisch et al, 2015), and there may be corresponding differences in the postcrania. If the two taxa can be differentiated in the postcranial region, this would suggest that there is a greater range of morphology than is presently recognized.…”

“…The posterior trunk region can similarly only be tentatively referred, but the material is identical to that of Cacops and can be differentiated from other olsoniforms on the basis of several features. Although Cacops is one of the better-known dissorophoids from the locality, its characterization has been based mostly on cranial material (Reisz et al, 2009;Fröbisch and Reisz, 2012;Fröbisch et al, 2015) and the anterior trunk region (Gee and Reisz, 2018). The newly described pelvis that we refer to the taxon is informative for expanding the characterized skeletal regions of the Richards Spur eucacopines.…”