Hemipristis intermedia Cicimurri, Ebersole, Stringer, Starnes & Phillips, 2025, sp. nov.
Creators: name: Cicimurri, David J.
name: Ebersole, Jun A.
name: Stringer, Gary L.
name: Starnes, James E.
name: Phillips, George E.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Elasmobranchii
Carcharhiniformes
Hemigaleidae
Hemipristis
Hemipristis intermedia

description: Hemipristis intermedia sp. nov.
urn:lsid:zoobank.org:act:25CF2AFD-3892-43EC-DE9878B39014
Fig. 6
Diagnosis
Upper lateral teeth are the most common tooth morphology represented, and because they are more diagnostic than the lower teeth, they are utilized herein to diagnose the species. Upper lateral teeth measure up to 2.5 cm in width (mesio-distal) and 2 cm in height (apico-basal). These teeth have a broad, triangular crown and distally directed main cusp. The mesial cutting edge may be smooth or bear up to ten denticles and the distal cutting edge up to 12 denticles, with denticles on both edges increasing in size towards the apex. A smooth-edged cusp constitutes the apical 30%–40% of the crown. Of the fossil Hemipristis species we consider valid, the upper lateral teeth of H. intermedia sp. nov. differ from those of the Eocene H. curvatus Dames, 1883 by attaining larger overall sizes (2.5 cm wide by 2.2 cm high for H. intermedia vs 1.5 cm and 1.1 cm, respectively for H. curvatus), by having more mesial and distal denticles (up to four and eight, respectively for H. curvatus, and up to 10 and 11, respectively, for H. intermedia), and by having mesial denticles that extend higher on the crown (two-thirds the crown height vs. one-half the crown height on H. curvatus). Hemipristis intermedia sp. nov. upper lateral teeth differ from those of the Miocene to Early Pleistocene H. serra Agassiz, 1835 by attaining smaller overall sizes (3.7 cm wide and 3.6 cm height for H. serra), by having fewer distal denticles (up to 20 have been observed on H. serra), and by having denticles that do not extent as close to the apex, resulting in a cusp that represents more than 20% of the crown height (as opposed to 10% in H. serra). These teeth are differentiated from those of the Rupelian H. tanakai Tomita, Yabumoto & Kuga, 2023 by having more than five mesial denticles (the maximum number reported for H. tanakai), and the apical-most mesial and distal denticles are of nearly equal height on the crown (whereas the distal denticle is generally higher in H. tanakai). Finally, the upper lateral teeth of Hemipristis intermedia sp. nov. differ from those of the extant H. elongata (Klunzinger, 1871) by being mesio-distally wider, by having more conspicuous denticles, and by having a more convex upper one-half of the mesial crown edge. The number of tooth denticles of Hemipristis intermedia is greater than the maximum occurring on H. curvatus teeth but less than the maximum number known for the Miocene to Early Pleistocene H. serra Agassiz, 1835. The proportion of cusp to total crown height is less than in H. curvatus but greater than in H. serra. The recently named H. tanakai (Tomita et al. 2023) is considered herein as a nomen dubium (see below), but the tooth size of that taxon overlaps with those of H. serra and H. intermedia. Additionally, only five mesial denticles occur in H. tanakai and the mesial denticles extend closer to the crown apex compared to the distal edge.
Etymology
The species name refers to the transitional tooth morphology between the Eocene Hemipristis curvatus and the Miocene to Early Pleistocene H. serra.
Material examined
Holotype
UNITED STATES OF AMERICA – Mississippi • upper left lateral tooth; Catahoula Formation; SC 2013.28.73 (Fig. 6 PP–RR).
Paratypes
UNITED STATES OF AMERICA – Mississippi • upper left anterior tooth; Catahoula Formation; MMNS VP-12037 (Fig. 6G–I) • lower left anterior tooth; Catahoula Formation; SC 2013.28.80 (Fig. 6P–R) • lower right lateral tooth; Catahoula Formation; MMNS VP-12036 (Fig. 6D–F).
Other material
UNITED STATES OF AMERICA – Mississippi • 189 isolated teeth; Catahoula Formation; MMNS VP-464 (2 teeth), MMNS VP-6625 (114 teeth), MMNS VP-6625.1 (Fig. 6 HH–JJ), MMNS VP-7243 (7 teeth), MMNS VP-7604 (Fig. 6 MM–OO), MMNS VP-7691 (9 teeth), MMNS VP-8745, MMNS VP-12035 (Fig. 6A–C), MMNS VP-12038 (Fig. 6J–L), MMNS VP-12039 (Fig. 6M–O), MMNS VP-12040 (Fig. 6S–U), MMNS VP-12041, MMNS VP-12042 (Fig. 6V–X), MMNS VP-12043 (Fig. 6Y – AA), MMNS VP-12044 (Fig. 6 BB–CC), MMNS VP-12045 (Fig. 6 DD–EE), MMNS VP-12046 (Fig. 6 FF–GG), SC 2013.28.69 to 28.72, SC 2013.28.74 to 28.79, SC 2013.28.81 to 28.89, SC 2013.28.90 (Fig. 6 KK–LL), SC 2013.28.91 to 28.101, SC 2013.28.102 (10 teeth), SC 2013.28.103 (Fig. 6 SS–TT), SC 2013.28.104 (Fig. 6 UU–VV), MMNS VP-7604 (Fig. 6 MM–OO).
Stratum typicum
Shelly, argillaceous sand of the Jones Branch fossil horizon, lower Catahoula Formation, Chattian Stage (horizon no longer accessible).
Locus typicus
Site MS.77.011, Jones Branch, tributary flowing into the Chickasawhay River, south of Waynesboro, Wayne County, Mississippi, USA.
Description
Several tooth morphologies are present, including specimens with a triangular, broad-based but apically narrow, slightly distally inclined crown. In profile view (Fig.6C, R, U), the crown on these teeth is flat to weakly sigmoidal, and the labial face is weakly convex, but the lingual face is strongly convex. The crown enameloid is smooth. In profile view, the mesial cutting edge is straight, and in labial/lingual view, it may be straight or concave basally but convex apically. The distal cutting edge is straight basally but overall exhibits a convex appearance due to the distally inclined cusp. The degree of curvature on these edges varies slightly. The mesial edge may be smooth along its entirety or bear up to nine denticles along its lower one- to two-thirds (compare Fig. 6B, E, H). These denticles are apically directed and decrease in size basally, but they do not reach the cusp apex and do not extend to the crown base. The distal edge bears up to nine denticles that decrease in size basally. These denticles do not reach the apex but can extend to the crown foot. The denticles are not serrated. The uppermost one-third of the crown is developed into a triangular cusp that varies slightly in width and degree of distal inclination (compare Fig. 6D to G). The mesial and distal cutting edges of the main cusp are smooth. The root is weakly bilobate with very short and diverging lobes that are separated by a narrow and shallow U-shaped interlobe area. A robust lingual boss (i.e., Fig. 6F) is bisected by a long, shallow but wide nutritive groove.
Other specimens are similar to those described above but have a broader crown that is more strongly distally curved. This broad-based and distally curved morphology is considered diagnostic of the species and a representative specimen was chosen as the holotype (Fig. 6 PP–RR). The largest tooth of this type measures 2.5 cm wide and 2 cm in total height. In profile view, the crowns of these teeth are labially curved and labio-lingually thin. The crown enameloid is smooth. The mesial edge is elongated and can be sinuous to uniformly convex (compare Fig. 6Y to 6DD), whereas the distal edge is uniformly concave along its length (i.e., Fig. 6T). The degree of curvature of the mesial and distal edges is variable. The mesial edge may be smooth, but it is more typically denticulated, often with 5–6 denticles, but up to ten may be present (compare Fig. 6 BB, FF, PP, S). These denticles are usually medially located on the edge, but they may only occur along the lower one-third or extend up to two-thirds of the crown height. Denticles are apically directed but decrease in size basally. The distal edge often bears eight denticles, but up to 11 can occur (compare Fig. 6 DD to T). Denticles are apically directed but decrease in size basally, and they extend to the crown foot. Although the distal denticles often extend higher onto the crown compared to the mesial denticles, the mesial denticles sometimes extend beyond the height of the distal ones (compare Fig. 6 EE to T). The apical portion of the crown is developed into a triangular cusp that is distally inclined to varying degrees. The mesial and distal cutting edges are smooth. The root is bilobate, with very wide but short sub-rectangular lobes. These are separated by a narrow U-shaped or V-shaped interlobe area. A low lingual boss (Fig. 6 AA) is bisected by a long, shallow, and wide nutritive groove.
Some specimens are quite distinct from both aforementioned morphotypes, as they are very narrow mesio-distally and have a tall crown (Fig. 6 HH). In profile view, the crown may be weakly sinuous, with strong lingual curvature and slight labial curvature of the crown faces (Fig. 6 JJ). The labial crown face is moderately convex and the lingual face very convex, which results in a somewhat conical crown. The crown may lack or have apical cutting edges, and no denticles are developed. The root is narrow, weakly bilobate, and has a robust lingual boss bearing a conspicuous nutritive groove. A more common morphology includes teeth with a wider crown that is denticulated. In profile view, the crown is highly lingually curved, and the labial face is convex basally but flatter apically (Fig. 6L, R). The lingual face is very convex, and crown enameloid is smooth on all specimens. The mesial side of the tooth may be rounded or bear a cutting edge that does not extend to the crown foot (Fig. 6 JJ). Relatively small and needle-like denticles can occur along the lower one-fourth of the mesial edge, of which up to three have been observed (Fig. 6Q). The distal edge usually bears a smooth cutting edge, which does not reach the crown foot. Two to four small and needle-like denticles occur at the lower one-third of the edge (Fig. 6M, P). The denticles on both sides of the crown are widely separated from each other and may be medially curved. The cutting edges are always smooth and may reach the level of the denticles. The denticle-free portion of the crown is a narrow and triangular cusp that is comparatively larger than those of previously described teeth. The root is bilobate with relatively short, diverging lobes, and the mesial lobe is more elongated and narrower than the distal lobe (Fig. 6H, Q). A robust lingual boss (Fig. 6O, R, JJ) is bisected by a deep but narrow nutritive groove.
Specimens SC 2013.28.103 (Fig. 6 SS–TT) and SC 2013.28.104 (Fig. 6 UU– VV) are diminutive teeth that are similar to each other. Both are broad-based and sub-triangular in labial view, with SC 2013.28.103 measuring 2 mm in width and SC 2013.28.104 just over 3 mm in width as preserved. Both specimens have an elongated and convex mesial cutting edge, and a much shorter (and smooth) distal cutting edge that intersect apically to form a rather small and distally inclined cusp. Although the mesial edge of SC 2013.28.104 is smooth, that of SC 2013.28.103 bears a diminutive denticle medially (compare Fig. 6 VV to TT). Each specimen has an oblique distal heel that bears four triangular denticles that decrease in size basally (Fig. 6 SS, UU). Overall, the crown of both specimens is rather straight, with the labial face being relatively flat and the lingual face convex. The crown foot of SC 2013.28.104 is not preserved, but that of SC 2013.28.103 is thickened and slightly overhangs the root. The root of SC 2013.28.103 is higher on the lingual side than on the labial side. The root lobes are very short, sub-rectangular, highly divergent, and separated by a very narrow U-shaped interlobe area. The lingual attachment surface is bisected by a conspicuous nutritive groove.
Specimens SC 2013.28.105, MMNS VP-7604, and MMNS VP-8745 are diminutive teeth of comparable morphology. The crowns measure 2.5 mm in width and 4 mm in height. Much of the crown is comprised of the main cusp, which is broad basally but rather needle-like apically. The conical cusp may lack cutting edges (Fig. 6 OO) or have mesial and distal cutting edges that are sharp, smooth, and extend to the base of the main cusp. Although the cusp is somewhat distally inclined, the mesial edge is concave and the distal edge is convex, which results in an unusual mesially directed cusp apex (Fig. 6 NN). The crown foot at the mesial and distal sides are formed into very short shoulders that each bear two denticles that decrease in size basally (Fig. 6 MM). The labial crown foot is very convex and there is a shallow but broad U-shaped embayment. The labial and lingual faces are smooth and convex.
Remarks
The tooth morphology of extant Hemipristis elongata (Klunzinger, 1871) is quite variable, and the teeth of the extinct H. curvatus Dames, 1883 and H. serra Agassiz, 1835 exhibit similar variation. These taxa, as well as the Catahoula Formation Hemipristis, exhibit monognathic and dignathic heterodonty. Ontogenetic heterodonty is also evident, as small teeth in our sample are similar to a tooth that Cicimurri & Knight (2009: fig. 5j) recovered from the Chattian Chandler Bridge Formation of South Carolina. That specimen lacks mesial serrations and was identified as a juvenile upper tooth of Hemipristis. Their interpretation is consistent with our evaluation of the Catahoula Formation Hemipristis sample, where upper teeth under 7 mm in width lack mesial serration. Specimens SC 2013.28.103, SC 2013.28.105, MMNS VP-7604, and MMNS VP-8745 are superficially like Paragaleus teeth, but our evaluation of four jaws of extant Hemipristis elongata (SC 84.177.1, SC 86.52.1, SC 2020.53.9, MSC 42627) leads us to conclude that they are teeth of very small individuals of H. intermedia sp. nov. Specimen SC 2013.28.103 (Fig. 6 SS–TT) is comparable to teeth in the postero-lateral files of H. elongata, whereas SC 2013.28.105 (Fig. 6 UU– VV), MMNS VP-7604 (Fig. 6 MM–OO), and MMNS VP-8745 are virtually identical to teeth in the lower anterior files.
Upper anterior teeth in the Catahoula Formation sample are identified by their triangular and rather weakly asymmetrical crown, whereas upper lateral teeth are broadly triangular with a conspicuous distally hooked appearance (compare Fig. 6G to S). Within lateral files, the amount of curvature of the mesial and distal edges, and the degree of distal cusp inclination increase towards the commissure (compare Fig. 6 PP to FF). Specimens believed to be lower symphyseal or parasymphyseal (i.e., Fig. 6 HH–JJ) teeth are very narrow with a roughly conical crown that lacks denticles and sometimes cutting edges. Lower anterior teeth are much narrower and bear significantly fewer denticles compared to upper anteriors, and the cusp constitutes a comparatively larger portion of the crown (Fig. 6J, P). The root of lower anterior teeth also has a more robust lingual boss compared to the upper teeth. Teeth from lateral positions are broader, have elongated cutting edges that reach the level of the mesial and distal denticles, and have up to five mesial and at least seven distal denticles. Based on our evaluation of extant H. elongata jaws (i.e., SC 84.177.1, SC 86.53.1), upper anterior teeth of H. intermedia sp. nov. are distinguished from lower lateral teeth by the greater number of mesial and distal denticles and the comparatively smaller proportion of main cusp to crown height (compare Fig. 6G to E). We chose an upper lateral tooth as the holotype specimen (Fig. 6 PP–RR) for the new species because, among the various fossil Hemipristis that have been named, this morphology is often the most common and easily identified.
The fossil record of Hemipristis extends back to the middle Eocene, with specimens of the globally widespread H. curvatus occurring as early as the Lutetian (NP15) (Ebersole et al. 2019). The species is well known from North America (i.e., White 1956; Westgate 1984; Parmley & Cicimurri 2003; Cicimurri & Knight 2019; Perez 2022) and Africa (i.e., Adnet et al. 2010, 2020; Underwood et al. 2011), with rare records from Asia (Tanaka et al. 2006; Tomita et al. 2023) and possibly Europe (Priem 1912; Ciobanu 1994). Hemipristis serra ranges from the Miocene to Early Pleistocene and was nearly globally distributed (Cappetta 2012). Hemipristis has also been reported from various Oligocene sites in the USA (Cicimurri & Knight 2009; Ebersole et al. 2021; Cicimurri et al. 2022) and Asia (Adnet et al. 2007), with specimens having been tentatively assigned to H. serra or altogether not speciated. Although Chandler et al. (2006) indicated that there was no evidence for the existence of Paleogene and Neogene species of Hemipristis other than H. curvatus and H. serra, Adnet et al. (2007) and Ebersole et al. (2021) suggested that Oligocene teeth represent a transitional species between the two.
Although the gross morphology of Hemipristis teeth has remained stable, even to the present day, large samples of H. curvatus teeth from the middle Eocene of Alabama (MSC collection), Bartonian of South Carolina (SC 2022.27) and Georgia (SC 2004.34, SC 2013.44), along with samples of H. serra from the Middle Miocene (Langhian) of North Carolina (contained within accession SC 98.46) and Gelasian (Early Pleistocene) of South Carolina (accessions SC 89.240, SC 2006.1), and jaws of extant H. elongata reveal significant differences among the various taxa. With respect to H. curvatus, H. intermedia sp. nov. attains a larger overall size (2.5 cm wide by 2.2 cm high vs 1.5 cm and 1.1 cm), and the latter species consistently has more extensively denticulated mesial and distal edges. Whereas the upper lateral teeth of H. curvatus exhibit fewer than four mesial and up to eight distal denticles, the teeth of H. intermedia have up to 10 mesial and 11 distal denticles. Additionally, the mesial denticles of H. curvatus are limited to the lower one-half of the crown, whereas they extend up to two-thirds of the crown height of H. intermedia. The cusp of H. curvatus teeth constitutes a larger proportion of the crown compared to H. intermedia. Variations in the number of mesial and distal denticles in H. curvatus and H. intermedia were also observed among the three jaws of H. elongatus, but the maximum number of denticles present and their distributions along the mesial and distal edges are taxonomically significant.
Hemipristis serra upper lateral teeth attain a significantly larger size than those of H. intermedia sp. nov., with the largest specimen available to us measuring 3.7 cm wide and 3.6 cm in height. In contrast, the largest tooth of H. intermedia sp. nov. in our sample measures only 2.5 cm and 2.2 cm in these dimensions, respectively. Additionally, the mesial and distal edges of H. serra teeth have a greater number of denticles, with at least 13 occurring on the distal side but more than 20 are common. On the mesial edge, the denticles are largest and most conspicuous along the upper one-half of the crown, but basally the edge appears more regularly serrated (serration/denticulation also consistently reaches the base of the edge). The denticles on H. serra teeth also extend closer to the apex, and the cusp comprises a very small portion of the crown compared to in H. intermedia. On the former, the cusp can represent as little as 10% of the total tooth height, whereas on the latter it represents at least 20%. Furthermore, small teeth of H. serra are as regularly serrated/denticulated as large teeth, whereas in H. intermedia these features are generally more extensive on large specimens.
Upper anterior teeth of each of the Paleogene and Neogene taxa are similar in gross morphology but can be separated based on the combination of maximum tooth size, degree of mesial denticulation and location of mesial denticles, degree of denticulation of the distal edge, and size of the cusp with respect to overall tooth size. The overall trend through time is an increase in maximum tooth size and number of mesial and distal denticles and a decrease in cusp size (in relation to total crown size). We found that the morphologies of lower anterior teeth of the Paleogene and Neogene taxa overlap and are largely differentiable by crown size and robustness. These teeth are not considered to be taxonomically useful for species determination.
For completeness, we also evaluated the teeth of extant H. elongata. All four H. elongata jaws we examined are of the same size and have similar tooth sizes, and none of the upper lateral teeth approach the largest H. curvatus in our sample (1 cm wide and 0.9 cm high vs 1.5 cm and 1.1 cm in these dimensions), let alone the largest H. intermedia sp. nov. tooth. In general, the upper lateral teeth of H. elongata are narrower and the mesial denticles (up to ten) are much less conspicuous compared to teeth of the extinct species. Additionally, the lower half of the tooth is the most convex, whereas it is most convex along the upper one-half on the fossil teeth. Interestingly, the cusp of H. elongata teeth constitutes slightly more than 20% of the total tooth height.
The Catahoula Formation Hemipristis teeth were compared to Oligocene specimens from the southeastern Atlantic Coastal Plain and Gulf Coastal Plain of the USA, including material from the Glendon Limestone Member of the Byram Formation of Alabama (Rupelian Stage, circa 30 Ma, NP23), the Old Church Formation of Virginia (Rupelian, roughly 29 Ma), the Ashley Formation of South Carolina (Rupelian, approximately 28.5 Ma), and the Chandler Bridge Formation of South Carolina (Chattian Stage, about 24.5 Ma). The Glendon Limestone Member specimen, documented by Ebersole et al. (2021), is a lower anterior tooth that is taxonomically uninformative beyond the generic level. Specimens from the Ashley Formation were identified as H. serra by Müller (1999) and Cicimurri et al. (2022). The specimens shown by Müller (1999: pl. 8 fig. 9) and Cicimurri et al. (2022: fig. 5a) are both comparable in size to the Catahoula Formation teeth, and the mesial edges are more extensively denticulated compared to in H. curvatus. Visually, the proportion of cusp to tooth height appears to be greater than that of H. serra. We examined five teeth from the Old Church Formation of Virginia that are included within accession SC 2020.43, as well as illustrations of four specimens provided by Müller (1999: pl. 8 figs 12–15). In general, the teeth are similar to those of the Catahoula Formation with respect to the number of denticles and the size of the cusp compared to overall tooth size. However, one specimen shown by Müller (1999: pl. 8 fig. 12) exhibits a large number of mesial/distal denticles and a relatively small cusp, features more consistent with H. serra. Ten teeth from the Chandler Bridge Formation contained within SC 2005.2 were examined, as were two specimens identified as H. serra by Cicimurri & Knight (2009). The Chandler Bridge Formation sample is variable and contains specimens that are similar to the Catahoula Formation teeth, as well as specimens that are comparable to H. serra (i.e., Cicimurri & Knight 2009: fig. 5i).
The Catahoula Formation Hemipristis teeth are comparable to Hemipristi s specimens from the Ashley Formation and, for the most part, the Old Church Formation. The Ashley and Old Church formations are slightly older than the Rupelian/Chattian Stage boundary, whereas the Catahoula Formation teeth are slightly younger than that boundary. The morphological and age similarities among the samples from these three units indicate that the Hemipristis teeth occurring in each unit are conspecific, and herein assigned to H. intermedia sp. nov. However, the Hemipristis teeth within the Chandler Bridge Formation, roughly four million years younger than the aforementioned units, are more similar to Miocene H. serra.
Adnet et al. (2007) reported a sample of 10 Hemipristis teeth from the Rupelian of Balochistan that they tentatively referred to H. serra. The two teeth they illustrated (figs 6, 15–17) are larger than and have more extensive mesial denticulation compared to Eocene H. curvatus, and they are smaller than and less denticulated than Miocene and younger H. serra. Those authors indicated that the teeth could represent a transitional morphology between the two species. The two teeth illustrated by Adnet et al. (2007) are both upper lateral teeth, and they fall within the range of variation we observed in the Catahoula Formation Hemipristis sample. However, as we found the dentition of the Catahoula Formation sample to be highly variable, we refrain from associating the Balochistan taxon with Hemipristis intermedia sp. nov. until other tooth morphologies (i.e., upper anterior and lower lateral teeth) can be examined and directly compared to those of the new species.
One additional taxon, H. tanakai Tomita, Yabumoto & Kuga, 2023, was recently erected based on a total of five teeth from widely disparate localities. The holotype is a complete tooth from the lower Oligocene (Rupelian) Yamaga Formation in Japan, and the paratype, a broken tooth preserved in labial view, may or may not be from the same lithostratigraphic unit and locality as the holotype. The authors also included in this species the specimens reported by Adnet et al. (2007) as well as a tooth from South Carolina. Unfortunately, this species may be considered a nomen dubium for several reasons. Firstly, one of the three criteria used to differentiate H. tanakai from other species is tooth height, which for H. tanakai is apparently at least 1.5 cm. We note here that although the total height in the H. curvatus we examined measured up to 1.2 cm, tooth height in H. serra can also measure 1.5 cm.Another characteristic attributed to H. tanakai is that the mesial edge purportedly bears up to five denticles. This morphology is comparable to that of H. curvatus, where the mesial edge may completely lack denticulation or have up to five denticles. The Catahoula Formation Hemipristis teeth, as well as those from the Old Church and Ashley formations (Müller 1999; Cicimurri et al. 2022) can have a far greater number of mesial denticles (8+), indicating that the fossils from these units are not conspecific with H. tanakai.
As mentioned earlier, Tomita et al. (2023: fig. 3) assigned a tooth from South Carolina to H. tanakai. Unfortunately, the stratigraphic occurrence of the specimen is listed as “(Upper Oligocene) Chandler Bridge Formation, Ashley Marl.” The Ashley Formation (Rupelian Stage) and Chandler Bridge Formation (Chattian Stage) are two different lithostratigraphic units separated by approximately five million years of time. Although the authors provided color images of the specimen (Tomita et al. 2023: fig. 3a–e), shark teeth from the Ashley and Chandler Bridge formations can have similar coloration (DJC, pers. obs.). Additionally, although the tooth shown has five distinct mesial denticles, there are several indistinct crenulations that could be counted as additional denticles (thereby increasing the number to at least seven and exceeding the number attributed to H. tanakai).
Thirdly, according to Tomita et al. (2023) the apical-most denticle on the mesial cutting edge in H. tanakai is located higher on the crown compared to the distal cutting edge. Although this may be true for the holotype specimen of H. tanakai shown by Tomita et al. (2023: fig. 2), it is not the case for the South Carolina specimen illustrated in their fig. 3a–e, and the mesial edge of their paratype specimen (fig. 3j) is not preserved. We suggest that the South Carolina specimen and broken paratype specimen be excluded from the H. tanakai hypodigm, as the stratigraphic and temporal occurrence of the former is ambiguous, and the latter specimen is poorly preserved (and only exposed from the matrix in labial view). Additionally, the morphological features attributed to H. tanakai are ambiguous and based only on the upper lateral morphology. In any event, the features of H. tanakai are inconsistent with those of the Catahoula Formation taxon (i.e., greater than ten mesial denticles, apical-most denticle of the distal edge is usually located higher than that on the mesial edge of the latter) and, if considered a valid species, does not appear to be conspecific with H. intermedia sp. nov.
description: Published as part of Cicimurri, David J., Ebersole, Jun A., Stringer, Gary L., Starnes, James E. & Phillips, George E., 2025, Late Oligocene fishes (Chondrichthyes and Osteichthyes) from the Catahoula Formation in Wayne County, Mississippi, USA, pp. 1-131 in European Journal of Taxonomy 984 (1) on pages 18-26, DOI: 10.5852/ejt.2025.984.2851, http://zenodo.org/record/15126034