Heptranchias Rafinesque, 1810
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https://doi.org/ 10.4202/app.01117.2023 |
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persistent identifier |
https://treatment.plazi.org/id/03E18741-1301-EF07-DC22-F8D7FB27FF56 |
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Felipe |
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Heptranchias Rafinesque, 1810 |
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Genus Heptranchias Rafinesque, 1810 View in CoL
Type species: Squalus perlo Bonnaterre, 1788 ; Recent, in temperate waters worldwide.
Heptranchias howellii (Reed, 1946)
Fig. 2C View Fig .
Material.—Four teeth: three (RU-EFP-03582, 4137, and 4138) from the MFL and one (RU-EFP-04139) collected as float. All from the Maastrichtian–Danian Hornerstown Formation, Edelman Fossil Park, Mantua Township, New Jersey, USA.
Description.—The principal cusp is fairly slender, apicodistally directed, and approximately twice as tall as the first few distal cusplets. The labial face of the principal cusp is nearly flat, whereas the lingual face is distinctly convex. The mesial and distal cutting edges of the principal cusp are nearly straight. Six mesial cusplets are present on each tooth. In the two nearly complete teeth, the first mesial cusplet is small and appears almost confluent with the mesial edge of the principal cusp, and it is followed by a larger, more distinct, second mesial cusplet. In the incomplete MFL specimen, the first mesial cusplet is large and distinct. Additional mesial cusplets steadily decrease in size. The mesial-most cusplet is directed mesially whereas succeeding cusplets turn to point apically then apicodistally as one follows their sequence up to the base of the principal cusp. The first three to four distal cusplets are roughly equal in breadth and height, while the final, distal-most cusplet is considerably smaller. Distal cusplets are directed apicodistally and exhibit roughly straight mesial and distal edges. The crown of RU-EFP-04138 has five distal cusplets, and RU-EFP-04139 has six. The basal border of the crown in these two specimens is slightly concave. The root is roughly rectangular in shape, with a pronounced mesial depression. In each tooth, the root is nearly as tall as the principal cusp, with a flat labial face and a rounded, mesio-distally directed ridge near the top of the lingual face. The basal border of RU-EFP-04139 (the only specimen with this edge complete) is flat.
Remarks.—The irregular decrease in size of the distal cusplets identify these teeth as belonging to Heptranchias ( Cappetta 1987) . Among described species, only Heptranchiashowellii is known to commonly have more than three mesial cusplets ( Welton 1974; Cappetta 1981; Adolfssen and Ward 2015); we therefore assign these teeth to that species. The Oligocene taxon Heptranchias ezoensis Applegate & Uyeno, 1968 , is known to possess three or fewer mesial cusplets ( Cappetta 1981; Carlsen and Cuny 2014), and Heptranchias tenuidens Leriche, 1938 , is now considered a likely synonym of H. howellii ( Cappetta 1987; Carrillo-Briceño et al. 2016).
Case (1973, 1980) mentioned the potential discovery of Heptranchias howellii from the Hornerstown Formation in Cream Ridge, New Jersey, which was viewed as suspect by Siverson (1995) based on similarity to teeth he described as Heptranchias sp. from the Danian of Sweden. We do not agree that the three features listed by Siverson (1995), namely slenderness of the principal cusp and sizes of the first distal and first mesial cusplets, readily distinguish any of these specimens from H. howellii . Rather, we find that the very subtle variations noted by Siverson (1995) to fit within the spectrum of morphologies in teeth attributed to H.howellii (e.g., Welton 1974; Cappetta 1987; Adolfssen and Ward 2015; Carrillo-Briceño et al. 2016). Thus, the specimens described here constitute a second recovery of H. howellii from the lower Hornerstown Formation of New Jersey and a new addition to the fauna of the EFPQ. Occurrence of two specimens in the MFL also indicates that H. howellii already existed in the earliest Danian, slightly older than other reports of Danian specimens from New Jersey ( Case 1980) and elsewhere ( Mannering and Hiller 2008).
Stratigraphic and geographic range.—Lower Paleocene (Danian) to lower Oligocene of Oregon and New Jersey in USA, Poland, and New Zealand.
Genus Hexanchus Rafinesque, 1810
Type species: Squalus griseus Bonnaterre, 1788 ; Recent, worldwide.
Fig. 2D View Fig .
Material.—Four lower lateral teeth: one (RU-EFP-02633) from the lower Hornerstown Formation above the MFL, three (RU-EFP-04140-1–04140-3) collected as float. All from the Maastrichtian-Danian Hornerstown Formation, Edelman Fossil Park, Mantua Township, New Jersey, USA.
Description.—The teeth are labiolingually narrow and, in lingual view, are low and mesiodistally elongate with up to nine distal cusplets (in the sole complete specimen). In all specimens where it is preserved, the principal cusp is modestly larger than the first distal cusplet, termed “grisiform” by Ward (1979), with a nearly straight and unserrated distal cutting edge. Fine serrations are present along the lower half of the mesial edge of the principal cusp. The tip of the principal cusp is broadly triangular and apicodistally directed. Distal cusplets decrease slowly and regularly in size and their tips are all directed apicodistally; their mesial edges are strongly convex, and their distal edges are weakly convex. The basal border of the crown is nearly straight, with only a very slight convexity developed beneath the principal cusp. The root is nearly twice as tall as the principal cusp and exhibits a distinct mesial depression. A longitudinal ridge traverses mesiodistally across the lingual face near the top of the root. The labial face of the root is flat, and its basal border is nearly straight and slightly angled to the basal border of the crown such that the root height decreases distally.
Remarks.—These teeth are assigned to Hexanchus based on their low, mesiodistally elongate form, fine serrations on the mesial cutting edge of the principal cusp, and distally-reducing distal cusplets ( Ward 1979). Serrations along the mesial cutting edge are larger in Notorynchus Ayres, 1855 ( Ward 1979) than in the specimens described here. Among the many species names ascribed to fossil Hexanchus teeth over the last 150 years, only two are generally still considered valid: H. microdon Agassiz, 1843 , and H. agassizi Cappetta, 1976 ( Adolfssen and Ward 2014, 2015). Adolfssen and Ward (2014) note that there are no appreciable anatomical differences among teeth of these two species and that they are normally used for Hexanchus material of different ages: H. microdon occurs in the Maastrichtian through the Danian whereas H. agassizi is restricted to the Eocene. Although the Danian age of the four specimens described here is hence more consistent with H. microdon , we refrain from assigning them to a particular species at this time because multiple authors note that tooth morphology in modern Hexanchus is known to vary ontogenetically, by gender, among individuals, and within the jaw (= monognathic heterodonty), and that, because of this, fossil species within the genus are in need of revision ( Adnet 2006; Adolfssen and Ward 2014, 2015).
Hexanchus sp. has previously been reported from the Paleocene–Eocene Vincentown, Manasquan, and Shark River formations in New Jersey ( Gallagher 1993) and from the MFL at the EFPQ by Gallagher ( Gallagher et al. 1986; Gallagher 1993); though his more recent faunal lists for the MFL have not included this taxon (perhaps by accidental omission in Gallagher 2002 and 2003?). Case (1996) also described several teeth he assigned to Hexanchus sp. and H. microdon from the lower Hornerstown Formation in “Deep Run” in Monmouth County, NJ. Recovery of at least one specimen from above the MFL extends Gallagher’s (1993) stratigraphic range for Hexanchus sp. in the EFPQ beyond the MFL into the upper Hornerstown Formation.
Genus Notidanodon Cappetta, 1975
Type species: Notidanus pectinatus Agassiz, 1843 ; Late Cretaceous , Sussex, England .
Notidanodon brotzeni ( Siverson, 1995)
Fig. 2E, F View Fig .
Material.—Three lower lateral teeth: two (RU-EFP-00244-1, 03586) from the MFL and one (RU-EFP-04141) collected as float. All from the Maastrichtian–Danian Hornerstown Formation, Edelman Fossil Park, Mantua Township, New Jersey, USA.
Description.—The principal cusp and distal cusplets are weakly convex both labially and lingually. In RU-EFP-04141 and 00244-1, the preserved principal cusp is broad, only slightly taller than the first distal cusplet, and apicodistally directed. It has a convex mesial edge and slightly concave distal edge. Mesial cusplets vary in number, with three present in the RU-EFP-03586, seven in RU-EFP-00244-1, and eight in the RU-EFP-04141. They are usually apicodistally directed, though the mesial-most mesial cusplets of the RU- EFP-00244-1 and 04141 are directed apically. The distal edges of both the mesial and distal cusplets are concave. Distal cusplets decrease slowly and regularly in size, and the basal border of the crown is distinctly convex beneath the principal cusp. The nearly complete root of RU-EFP-03586 is mesiodistally wide, decreases in height distally, and would have been roughly two to three times as tall as the principal cusp if it were complete. A pronounced horizontal ridge traverses the lingual face of the root of both RU-EFP-03586 and 04141, roughly one-third of the way down from the basal border of the crown. Apicobasally oriented ridges are present on the labial face of the root and are roughly positioned such that they descend beneath the notches between each cusp of the crown. A mesial depression is present in the root of both as well.
Remarks.—The combination of distal cusplets that regularly decrease in size from a modestly large acrocone that exhibits multiple, distinct, large cusplets along its mesial edge identify these specimens as belonging to the genus Notidanodon ( Cappetta 1987; Siverson 1995). As in all known species except N. loozi Vincent, 1876 , the mesial cusplets are apicodistally directed ( Ward 1979; Ward and Thies 1987; Siverson 1995). The distal cutting edges of the principal cusp and mesial cusplets are slightly concave, similar to those of N. brotzeni , N. pectinatus Agassiz, 1843 , and N. dentatus Woodward, 1886 , but in contrast to those of N. loozi and N. lanceolatus Woodward, 1886 , which are convex Ward 1979; Cione and Medina 1987; Siverson 1995). Also as in N. brotzeni , the basal border of the crown in these specimens is distinctly convex beneath the principal cusp; this differs from N. dentatus and N. pectinatus which exhibit a flatter border ( Ward and Thies 1987; Siverson 1995). N. dentatus and N. loozi also generally tend to exhibit fewer and larger distal cusplets ( Ward 1979; Cione and Medina 1987) than in the specimens described here. Similar to N. brotzeni and N. loozi , the mesial margins of the principal cusp and distal cusplets are convex, whereas in N. lanceolatus they are nearly straight ( Ward and Thies 1987; Siverson 1995). The proportionately tall root seen in our specimens compares best with the tall roots of N. brotzeni and N. loozi Siverson 1995 ; Cappetta 1987; Ward and Thies 1987).
To summarize, among known species of Notidanodon , the EFPQ specimens share the most similarities with N. brotzeni . These features include apicodistally directed mesial cusplets, slightly concave distal edges of the principal cusp and mesial cusplets, a convex basal borderline of the crown, and convex mesial margins of the principal cusp and distal cusplets ( Siverson 1995). We therefore assign the specimens to N. brotzeni , and further note that N. brotzeni is also the only one of the five known species reported from the Danian, the same age as the majority of the Hornerstown Formation at the EFPQ.
Notidanodon brotzeni was previously only known from the middle Danian of Sweden and Denmark ( Siverson 1995), with a second possible occurrence later in the Paleocene of New Zealand ( Mannering and Hiller 2008). The three specimens described here represent the first occurrence of N. brotzeni in the Western Hemisphere. Further, occurrence of two of the new specimens in the MFL demonstrates that N. brotzeni existed in the very beginning of the Danian and most likely evolved in the Maastrichtian, if not earlier.
Stratigraphic and geographic range.—Lower Paleocene Danian) of New Jersey in USA, Denmark, Sweden, and Morocco.
Genus Weltonia Ward, 1979
Type species: Notidanus (Heptranchias) ancistrodon Arambourg, 1952 , Thanetian , Ouled Abdoun basin, Morocco .
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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Heptranchias Rafinesque, 1810
| Boles, Zachary M., Ullmann, Paul V., Putnam, Ian, Ford, Mariele & Deckhut, Joseph T. 2024 |
Weltonia
| Ward 1979 |
Notidanodon
| Cappetta 1975 |
H. microdon
| Agassiz 1843 |