Hemipristis intermedia Cicimurri, Ebersole, Stringer, Starnes & Phillips, 2025, sp. nov.

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 na