Early Oligocene (Rupelian) fishes (Chondrichthyes, Osteichthyes) from the Ashley Formation (Cooper Group) of South Carolina, USA
Author
Cicimurri, David J.
Author
Knight, James L.
Author
Ebersole, Jun A.
text
PaleoBios
2022
2022-03-31
39
1
1
38
http://dx.doi.org/10.5070/p939056976
journal article
10.5070/P939056976
0031-0298
13743778
13E6A6E9-DE0F-4C71-BE40-2957F48D9F70
“
DASYATIS
” SP.
FIG. 7V
–CC
Type
species
—
Dasyatis ujo
Rafinesque, 1810a
; Recent.
2009a
Dasyatis rugosa
(
Probst, 1877
)
; Cicimurri and Knight, page 638, fig. 8C.
Referred specimens (n=11)
—SC2007.36.49 (
Fig. 7V
–CC1), SC2007.36.50 (three teeth), SC2007.36.51 (
Fig. 7T–U
), SC2007.36.225, SC2015.29.14, SC2015.29.43, SC2015.29.44, SC2015.29.45 (
Fig. 7V–Y
), SC2015.29.46.
Remarks
—These teeth differ from those of “
Taeniurops
”
cavernosus
discussed above by having a more convex labial face, a more angular labial crown margin (as opposed to uniformly convex), and a wider transverse crest that is crenulated. The Ashley Formation specimens are ablated but appear to be conspecific with teeth occurring in the overlying Chandler Bridge Formation identified as
Dasyatis rugosa
(
Probst, 1877
)
by
Cicimurri and Knight (2009a)
. Reinecke (2015) noted differences between the Chandler Bridge teeth and
D. rugosa
from
Germany
, and he indicated an early Chattian first appearance for this species.
Reinecke et al. (2011)
illustrated (plate 96, fig. 4) one of
Probst’s (1877)
original specimens of
D. strangulata
, and the species was also reported by
Reinecke et al. (2014)
and
Reinecke and Radwański (2015)
. The South Carolina specimens do appear to have a more convex labial face with less robust ornamentation, and they are more similar to
D. strangulata
than to
D. rugosa
in these respects (
Reinecke et al. 2011
,
Reinecke et al. 2014
,
Reinecke and Radwański 2015
).
Although teeth with this morphology have traditionally been placed within
Dasyatis
(see
Cappetta 2012
), recent molecular studies of extant species revealed the genus to be paraphyletic (
Last et al. 2016
,
Nelson
et al. 2016
). This prompted the referral of many extant
Dasyatis
species
to various other genera, like
Bathytoshia
Whitley, 1933
,
Fontitrygon
Last et al., 2016
,
Hemitrygon
Müller and Henle, 1838
,
Hypanus
Rafinesque, 1818
,
Megatrygon
Last et al., 2016
, and
Telatrygon
Last et al., 2016
. Because a comparative study of the dentitions of these extant taxa has yet to be undertaken, we herein conservatively retain this species within
Dasyatis
with the understanding that they may someday be referred to one of the aforementioned extant genera, or perhaps to an unknown fossil taxon. The Ashley Formation specimens are morphologically similar to
D. strangulata
, a taxon that has tentatively been identified from the late Chattian by
Reinecke et al. (2014)
. However, we refrain from assigning the
South Carolina
specimens to this species due to their much older occurrence compared to the typically Miocene range of
D. strangulata
.