DOI: 10.15468/yszdr8
title: Two new species of Mennerotodus Zhelezko, 1994 (Chondrichthyes: Lamniformes: Odontaspididae), from the Paleogene of the southeastern United States

description: This dataset contains the digitized treatments in Plazi based on the original journal article Cicimurri, David J., Ebersole, Jun A., Martin, George (2020): Two new species of Mennerotodus Zhelezko, 1994 (Chondrichthyes: Lamniformes: Odontaspididae), from the Paleogene of the southeastern United States. Fossil Record 23 (2): 117-140, DOI: 10.5194/fr-23-117-2020, URL: http://dx.doi.org/10.5194/fr-23-117-2020Abstract. Mennerotodus Zhelezko, 1994, is an extinct lamniform shark known to occur in Paleogene strata of the Tethyan region of Asia and Europe. Although only a single species has been named, multiple subspecies have been erected and used as biostratigraphic tools in Asia. The genus has not been reported with confidence outside of the Tethyan region, but we have identified two new species of Mennerotodus from Paleogene deposits of the southeastern United States. Mennerotodus mackayi sp. nov. is described by teeth occurring in the lower Paleocene (Danian Stage) Pine Barren Member of the Clayton Formation of southern Alabama. A middle Eocene (Bartonian) species, Mennerotodus parmleyi sp. nov., is based on material occurring in the Clinchfield Formation in central Georgia. The early Paleocene record could indicate a North American origin for Mennerotodus relatively soon after the K–Pg event, with subsequent radiation to other parts of the world. The genus is likely more widely distributed than is currently known, but teeth can easily be overlooked due to their similarity to other taxa.1 IntroductionMennerotodus Zhelezko, 1994, is an extinct odontaspidid shark that was originally named based on middle Eocene (Bartonian) teeth from Kazakhstan. The teeth were distinguished by their overall shape and the development of denticulation at the base of the main cusp. Although the genus Mennerotodus was named by Zhelezko in 1989 (p. 17), no type specimens were designated, nor were any specimens illustrated in this original publication, so the generic name was therefore a nomen nudum. Zhelezko (in Zhelezko and Kozlov, 1990, p. 175) used the name again soon thereafter, but the genus was not formally recognized until teeth were described and figured by Zhelezko in 1994. Zhelezko (1994) erected three species of Mennerotodus, but only the type species, M. glueckmani Zhelezko, 1994, is currently recognized (Cappetta, 2012). Within this species, Zhelezko (1994) named three subspecies, including M. g. glueckmani, M. g. usunbassi, and M. g. boktensis. There was an intent to utilize the subspecies as biostratigraphic tools, as the type stratum for M. g. boktensis is the middle Eocene (Lutetian) Amankisilit Formation, M. g. glueckmani is from the lower Shorym Formation (Bartonian), and M. g. usunbassi was in the upper Shorym Formation (Bartonian; Zhelezko, 1994). Cappetta (2012) reported the temporal distribution as late Paleocene (Thanetian) to late Eocene (Priabonian).The two other Mennerotodus species, M. borealis Zhelezko, 1994, and M. karpinsky (Menner, 1928), are no longer considered to belong to this genus. These species were later moved to the genus Borealotodus Zhelezko and Kozlov, 1999, and apparently the subtle differences between Borealotodus and Mennerotodus were not evident when the morphologies were originally described. Malyshkina (2006a) concluded that Borealotodus karpinsky (Menner, 1928) is a junior synonym of Mennerotodus glueckmani, but Cappetta (2012) maintained B. karpinsky to be valid. Cappetta (2012) noted the similarities between Borealotodus and Mennerotodus but concluded that the genera were distinguished by their anterior teeth. According to Cappetta (2012), Mennerotodus anterior teeth differ from those of Borealotodus in being more sigmoidal and lingually curved in profile view, and the main cusp is narrower basally and more sharply tapered apically.Figure 1. Generalized location and surface stratigraphy of site ALn-13, Lowndes County, AL, USA. (a) Geographic maps showing the location of site ALn-13 in country, state, and county contexts. (b) Danian surface stratigraphy in Alabama, USA. Shaded areas on the stratigraphic chart represent unconformities.Dutheil et al. (2006) identified Mennerotodus in Thanetian deposits of the Paris Basin, thereby extending the geographic range of the genus to western Europe. Although the authors did not attribute the material to any species, they observed that the teeth were relatively common. Ebersole et al. (2019) were the first to recognize the genus in North America based on a sample of middle Eocene (Bartonian) specimens from southern Alabama.Herein we describe two new species of Mennerotodus from Paleogene strata of the southeastern United States. The older of the two species was recovered from the lower Paleocene (Danian Stage) Pine Barren Member of the Clayton Formation of southeastern Alabama (Fig. 1a). The other species derives from the middle Eocene (Bartonian–Priabonian) Clinchfield Formation in central Georgia (Fig. 2a). We also provide additional morphological features that allow for differentiation of Mennerotodus from similarly shaped teeth of other, coeval genera. Heterodonty within the two new species is discussed, and artificial dentitions of each species are presented. In addition, we comment on the paleobiogeographic and stratigraphic distribution of Mennerotodus in North America.