Negaprion gilmorei ( White, 1956 ),

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L., 2019, Taxonomy and biostratigraphy of the elasmobranchs and bony fishes (Chondrichthyes and Osteichthyes) of the lower-to-middle Eocene (Ypresian to Bartonian) Claiborne Group in Alabama, USA, inclu, European Journal of Taxonomy 585, pp. 1-274: 73-77

publication ID

https://doi.org/10.5852/ejt.2019.585

publication LSID

lsid:zoobank.org:pub:181B6FBA-ED75-4BB4-84C4-FB512B794749

DOI

http://doi.org/10.5281/zenodo.3664595

persistent identifier

http://treatment.plazi.org/id/18174D41-FFCD-FFE3-FD8B-9B974CF108DC

treatment provided by

Plazi

scientific name

Negaprion gilmorei ( White, 1956 )
status

 

Negaprion gilmorei ( White, 1956) 

Fig. 27View Fig

Sphyrna gilmorei Leriche, 1942: 47  , pl. 4, fig. 1.

Alopias latidens alabamensis White, 1956: 132–133  , text figs 28–32, pl. 2, figs 5–6.

Negaprion gibbesi gilmorei White, 1956: 142  , figs 37–66, pl. 2, fig. 9.

Hypoprion greyegertoni White, 1956: 137  , figs 50–56, pl. 2, fig. 7.

Aprionodon greyegertoni – Thurmond & Jones 1981: 65  , fig. 30.

Negaprion gibbesi gilmorei – Thurmond & Jones 1981: 66  , fig. 31.

Carcharhinus greyegertoni – Kruckow & Thies 1990: 51  .

Carcharhinus gilmorei – Müller 1999: 49  , pl. 7, fig. 1.

Sphyrna  sp. – Cappetta & Case 2016: 61, pl. 10, figs 1–4.

Material examined

UNITED STATES OF AMERICA – Alabama • 1519 isolated teeth; Claiborne Group ; ALMNH PV1989.4.13.3 (25 specimens), ALMNH PV1989.4.151.1b, ALMNH PV1989.4.193, ALMNH PV1989.4.196 (21 specimens), ALMNH PV 1989.4.6 (2 specimens), ALMNH PV1989.4.8.3 (17 specimens), ALMNH PV1989.4.8.4 (18 specimens), ALMNH PV1993.2.401 (160 specimens), ALMNH PV1993.2.402 (50 specimens), ALMNH PV2016.3.72, ANSP 23422View Materials, GSA-V701 (5 specimens), GSA-V704 (2 specimens), GSA-V710, MSC 188.3 5, MSC 188.7 10, MSC 188.14, MSC 188.24 25, MSC 188.28, MSC 188.30, MSC 188.33, MSC 188.35, MSC 188.37, MSC 188.46 48, MSC 188.52 53, MSC 188.55 59, MSC 188.61, MSC 188.63 64, MSC 188.66, MSC 188.69 71, MSC 188.74 77, MSC 188.80 81, MSC 188.83 87, MSC 188.90 93, MSC 188.95, MSC 188.97 100, MSC 188.102 103, MSC 188.105 106, MSC 188.108 110, MSC 188.113 116, MSC 188.118 119, MSC 188.122, MSC 188.125, MSC 188.127, MSC 188.132 135, MSC 188.137 139, MSC 188.141 144, MSC 188.146 148, MSC 188.150, MSC 188.152 157, MSC 188.160 163, MSC 188.165, MSC 188.167 168, MSC 188.170 173, MSC 188.175, MSC 188.177, MSC 188.180 184, MSC 188.186 187, MSC 188.189 192, MSC 188.194 196, MSC 188.198 201, MSC 188.203, MSC 188.206, MSC 188.208 216, MSC 188.218 224, MSC 188.226 232, MSC 188.234 240, MSC 188.242 244, MSC 188.246 253, MSC 188.256 257, MSC 188.260, MSC 188.264 265, MSC 188.267, MSC 188.269 271, MSC 188.274, MSC 188.277, MSC 188.279, MSC 188.281, MSC 188.284 291, MSC 188.293 296, MSC 188.298 302, MSC 188.304, MSC 188.306, MSC 188.309, MSC 188.312 315, MSC 188.319 322, MSC 188.325, MSC 188.327, MSC 188.329, MSC 188.332 336, MSC 1424.3 8, MSC 1424.13 21, MSC 2171.7, MSC 2173.8, MSC 2175.1 4, MSC 2175.7 8, MSC 2175.10 16, MSC 2175.18, MSC 2175.20, MSC 2175.23 24, MSC 2175.26 29, MSC 2175.31 37, MSC 2175.41 48, MSC 2175.50 54, MSC 2175.56, MSC 2175.58 63, MSC 2175.65 69, MSC 2175.71 73, MSC 2380.1 19, MSC 37161.1 16, MSC 37395, MSC 37431, MSC 37466.1 62, MSC 37469, MSC 37475, MSC 37493.1 552, MSC 37526.1 2, MSC 37539.1 3, MSC 37545, MSC 37593, MSC 37594, MSC 37596.1 134, MSC 37597.1 6, MSC 37649View Materials, MSC 37682.1 5, MSC 37914.1 5, MSC 37916.1 2, MSC 38415.1 6, MSC 38429, MSC 38465, MSC 38466.1 29, MSC 38495.1 6, MSC 38506.1 11, MSC 38508.1 10, MSC 38547.1 33, MSC 38547.9, MSC 38556.1 8, NJSM 24029View Materials, SC 2012.47.165 (4 specimens), SC 2012.47.176, SC 2012.47.181  .

Description

Dentition exhibits strong dignathic heterodonty. Upper anterior teeth with triangular main cusp. Broadbased cusp flanked by short, oblique mesial and distal heels. Lateral teeth mesiodistally wider, cusp distally inclined, shoulders more elongated, becoming horizontal. Posterior teeth wide, short and distally inclined cusp. Cutting edges on cusp smooth; cutting edges on shoulders smooth to weakly and irregularly serrated. Labial crown face flat; lingual face convex; smooth enameloid. Root bilobate; lobes elongated, low, rounded, highly diverging. Interlobe area generally shallow, V-shaped. Attachment surface of lingual face generally flat, bisected by deep nutritive groove. Nutritive groove often forms a distinctive basal notch. Lower anterior teeth with narrow, erect cusp flanked by short, nearly horizontal mesial and distal shoulders. Lateral teeth mesiodistally wider, with distally inclined cusp, elongated lateral shoulders. Posterior teeth with shorter and very inclined cusp. Cutting edges of cusp and shoulders smooth.

Remarks

Woodward (1889) erected the name Carcharias (Aprionodon) gibbesii  for 120+ teeth he examined in the NHMUK collections that were derived from Eocene deposits in South Carolina and Clarke County, AL. Although Woodward (1889) did not figure these teeth, with some uncertainty he referred several of those illustrated by Gibbes (1848) to his new taxon, whereas others he identified as Galeocerdo minor Agassiz, 1843  ( Gibbes 1848: pl. 25, figs 63–65), and a single specimen was assigned to Oxyrhina minuta Agassiz, 1843  ( Gibbes 1848: pl. 27, fig. 164).

White (1956) later reexamined Woodward’s (1889) Carcharias (Aprionodon) gibbesii  teeth and agreed that Gibbes’ (1848: pl. 27, fig. 164) Oxyrhina minuta  was a lower tooth of the gibbesii  morphology. However, of Gibbes’ (1848: pl. 25, figs 63–65) Galeocerdo minor  teeth, White (1956) disagreed with Woodward’s (1889) referral and said they belonged instead to Sphyrna prisca (Agassiz, 1843)  . White (1956) assigned the gibbesi  morphology to Negaprion  because he believed that they more closely resembled teeth of the extant Lemon Shark. However, several years prior, Leriche (1942: 47, pl. 4, fig. 1) figured two teeth from the Priabonian Yazoo Clay at Cocoa in Choctaw County, AL that he referred to a new taxon, Sphyrna gilmorei  , noting their similarity with the extant Sphyrna prisca  . White (1956) reexamined these teeth and synonymized S. gilmorei  with Negaprion gibbesii  . White (1956) also noted slight differences between Woodward’s (1889) South Carolina and Alabama teeth and stated that the South Carolina specimens had finer serrations on the upper teeth, and to some extent on the lower teeth, whereas the lower teeth from Alabama were smooth. Because of this, White (1956) referred to the South Carolina teeth as the “typical” form Negaprion gibbesii  , and assigned the Alabama teeth to a new subgenus, Negaprion gibbesii gilmorei  . White’s (1956) placement of these morphologies within Negaprion  was later followed by numerous authors, including Case (1980), Thurmond & Jones (1981), Westgate (1984), and Krukow & Thies (1990).

Based on nine teeth from Clarke County, AL, White (1956) erected the taxon Hypoprion greyegertoni  , which Thurmond & Jones (1981) later placed within Aprionodon  because this genus lacked the lateral cusplets that occur on the teeth of Hypoprion  . Thurmond & Jones (1981) also stated that the teeth of Aprionodon greyegertoni  were very similar to those of Negaprion gibbesi gilmorei  but differed by being taller than broad and lacking a medial nutritive groove (stating this characteristic was very prominent on the teeth of N. gibbesi gilmorei  ). Müller (1999), however, noted issues with White’s (1956) H. greyegertoni  syntypes and believed that they represented at least three different genera. Müller (1999) designated H. greyegertoni  as a nomen dubium, referred most of White’s (1956) syntypes to the genera Abdounia  and Physogaleus  , and assigned White’s (1956: figs 50–51, 53–54, 56) remaining teeth to the gilmorei  morphology.

Ward & Wiest (1990) and Müller (1999) both recognized teeth of the gibbesi  morphology as occurring within the Paleocene-to-Eocene Pamunky Group in Maryland, and Müller (1999) reported both the gibbesi  and gilmorei  morphologies from the same deposits in Virginia. Ward & Wiest (1990) and Müller (1999) placed these morphologies within the genus Carcharhinus  , and between the two, elevated both C. gibbesi  and C. gilmorei  to species status. Manning (2003) later suggested that these two species are intergradational, with C. gilmorei  occurring in both Eocene and Oligocene deposits, whereas C. gibbesi  was largely confined to the Oligocene.

As part of our study, we examined numerous teeth of the gilmorei  / gibbesi  morphologies that were derived from various middle Eocene (Lutetian) to late Oligocene (Chattian) localities in Alabama. We determined that all these teeth represent the gilmorei  morphology, as serrations on the upper and lower teeth were either absent or inconspicuous.Although no teeth attributable to the gibbesi  morphology (those with distinct heel serrations) were identified in our sample, the presence of the gilmorei  morphology within both Eocene and Oligocene deposits in Alabama corroborates Manning’s (2003) observation regarding the stratigraphic range of this species.

To further complicate the matter, Cappetta & Case (2016) identified 40 specimens from the contact of the Tallahatta and Lisbon formations at site ACov- 11 in Covington County as belonging to Sphyrna  sp. and suggested these teeth represented the oldest occurrence of this genus. Cappetta & Case (2016: pl. 10, figs 1–4), however, failed to compare the teeth in their sample to those with the gilmorei  morphology, even though the specimens they figured are conspecific with the upper teeth of this taxon. Furthermore, our sample consisted of 23 additional specimens from the ACov-11 locality that appear conspecific to those figured by Cappetta & Case (2016), all of which are consistent with the gilmorei  morphology.

Confusion over the generic placement of teeth with the gilmorei  morphology stems from the generalized dentition of this shark, which consists of T-shaped lower teeth and upper teeth with a broader triangular main cusp.This generalized dentition strongly resembles those of several representatives within the extant Carcharhinus  , Negaprion  , and Sphyrna  , prompting various authors, at one point or another, to refer the gilmorei  morphology to each of these genera (see Leriche 1942; White 1956; Müller 1999). To garner insight into the taxonomic placement of teeth with the gilmorei  morphology, we compared the teeth in our sample to those within the dentitions of extant representatives within all three of the aforementioned genera. Our observations show that the dentitions of the numerous species of Carcharhinus  are extremely variable in terms of upper and lower tooth morphology, but all members of the genus can be categorized by having distinct dignathic heterodonty with upper teeth having serrated mesial and distal cutting edges, and lower teeth with more slender crowns that may or may not have weak serrations (see Voigt & Weber 2011). A few Carcharhinus  species have lower teeth that bear fine serrations extending nearly to the apex of the crown (i.e., C. acronotus  , C. albimarginatus  , C. amblyrhynchos  , C. amboinensis  , C. borneensis  , C. brachyurus  , C. leucas  , C. longimanus  , and C. wheeleri  ), whereas other species have weak serrations that are confined to the mesial and distal shoulders (i.e., C. hemiodon  , C. obscurus  , C. porosus  , C. signatus  ). However, the upper teeth of all these species have serrated mesial and distal cutting edges, with serrations generally extending nearly to the crown apex.

The Sphyrnidae  ( Eusphyra  and Sphyrna  ) jaw sets we examined exhibited varying degrees of dignathic heterodonty (see Compagno 1984) and fall into one the following four categories: 1) those with triangular upper teeth and lower teeth with a narrow crown and a sinuous mesial edge (i.e., Eusphyra blochii  and Sphyrna tiburo  ); 2) those with upper and lower teeth with a narrow crown and a sinuous mesial edge (i.e., Sphyrna corona  ); 3) those with triangular upper teeth and T-shaped lower teeth (i.e., Sphyrna lewini  , Sphyrna media  , and Sphyrna tudes  ); and 4) those with triangular upper and lower teeth exhibiting little dignathic heterodonty (i.e., Sphyrna mokarran  and Sphyrna zygaena  ). Of these species, S. tudes  had serrated cutting edges on its upper teeth but smooth cutting edges on the crowns of lower teeth, and upper and lower teeth of S. mokarran  are uniformly serrated. All remaining species have upper and lower teeth that lack serrations.

The dentitions of the two extant species of Negaprion  , N. acutidens  and N. brevirostris  , exhibit a similar degree of dignathic heterodonty, consisting of triangular upper teeth and T-shaped lower teeth. Both species also have serrated upper teeth, although to varying degrees. The upper teeth of N. acutidens  have serrated mesial and distal cutting edges, and the serrations extend almost to the cusp apex. In contrast the serrations on upper teeth of N. brevirostris  are confined to the mesial and distal shoulders and do not extend onto the central cusp. The cutting edges on the lower teeth of both species are smooth. Examination of teeth from the extinct N. eurybathodon  show they are more similar to those of N. brevirostris  , with a difference being the occasional presence of weak serrations on the mesial and distal shoulders on certain lower teeth of the extinct species.

Although early Carcharhinus  representatives have been recently described from middle and upper Eocene deposits elsewhere (see Adnet et al. 2007; Underwood & Gunter 2012; Samonds et al. 2019), these species, as well as all the extant species, have upper teeth with serrations on their mesial and distal cutting edges that extend nearly to the apex of the crown. The presence of these mesial and distal serrations appears to be a defining characteristic of Carcharhinus  (see Underwood & Gunter 2012), suggesting teeth with the gilmorei  morphology do not belong to this genus. Assigning the gilmorei  morphology to Sphyrna  is also problematic because molecular divergence estimates by Lim et al. (2010) indicated that the family Sphyrnidae  split from Carcharhinus  during the early-to-middle Eocene (40 to 50 Ma), and that Sphyrna  only diverged from its sister taxon Eusphyra  during the early-to-middle Miocene (15 to 20 Ma). These data suggests that true members of Sphyrna  did not evolve until the earlyto-middle Miocene, and any Eocene teeth with a similar morphology should therefore be referred to a different genus. Regarding the use of Negaprion, Schultz et al. (2008)  calculated molecular divergence times for the two extant species of the genus and suggested that they are derived from a cosmopolitan common ancestor, the Oligo–Miocene Negaprion eurybathodon (Blake, 1862)  .

Our analysis showed that extant species of Carcharhinus  , Sphyrna tudes  , and Negaprion acutidens  have teeth with serrations that extend nearly to the apex of the crown in all upper tooth positions. In addition, all the species within the Sphyrnidae  (with the exception of S. tudes  and S. mokarran  ) were observed to have smooth crowns on both the upper and lower teeth. Based on these observations, teeth with the gilmorei  morphology appear most closely aligned with those of N. brevirostris  and N. acutidens  in that they have triangular upper teeth, T-shaped lower teeth, and weak serrations that are limited to the mesial and distal shoulders of certain teeth (as serrations appear on the upper teeth in N. brevirostris  and both upper and lower teeth in N. acutidens  ). Due to their morphological similarity to the other members of Negaprion  , we concur with previous assignments of the gilmorei  morphology to Negaprion  , making N. gilmorei  one of the earliest representatives of the genus.

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the contact of the Tallahatta and Lisbon formations at sites ACh-14, ACov-11 and ACon-6, the basal Lisbon Formation at site ACov-11, the “upper” Lisbon Formation at site ACl-3, the contact of the Lisbon Formation and Gosport Sand at site AMo-4, the basal Gosport Sand at site ACl-4, and the Gosport Sand at site ACh-21. Lower Lutetian to middle Bartonian, zones NP14 to NP17.

ALMNH

Alabama Museum of Natural History

Kingdom

Animalia

Phylum

Chordata

Class

Elasmobranchii

Order

Carcharhiniformes

Family

Carcharhinidae

Genus

Negaprion

Loc

Negaprion gilmorei ( White, 1956 )

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L. 2019
2019
Loc

Sphyrna gilmorei

Leriche M. 1942: 47
Loc

Negaprion gibbesi gilmorei

White E. I. 1956: 142
Loc

Hypoprion greyegertoni

White E. I. 1956: 137
Loc

Aprionodon greyegertoni – Thurmond & Jones 1981: 65

Thurmond J. T. & Jones D. E. 1981: 65
Loc

Negaprion gibbesi gilmorei – Thurmond & Jones 1981: 66

Thurmond J. T. & Jones D. E. 1981: 66
Loc

Carcharhinus greyegertoni –

Kruckow T. & Thies D. 1990: 51
Loc

Carcharhinus gilmorei – Müller 1999: 49

Muller A. 1999: 49
Loc

Sphyrna

Cappetta H. & Case G. R. 2016: 61