Mennerotodus parmleyi, Cicimurri & Ebersole & Martin, 2020
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https://doi.org/ 10.5194/fr-23-117-2020 |
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https://doi.org/10.5281/zenodo.11617155 |
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https://treatment.plazi.org/id/03C7E527-FFBC-FFF9-FC88-FD52FF5C588D |
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Felipe |
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scientific name |
Mennerotodus parmleyi |
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sp. nov. |
Mennerotodus parmleyi sp. nov.
LSID urn:lsid:zoobank.org:act:36F949AD-0166-453CAEB9-5805B7E9A141
1984 Odontaspis hopei, Westgate , p. 358, fig. 3a.
2003 Carcharias accutissima, Parmley and Cicimurri , fig. 3e.
2003 Carcharias acutissima, Parmley and Cicimurri , p. 160– 161.
2003 Carcharias hopei, Parmley and Cicimurri , p. 161–162, fig. 3f.
2019 Mennerotodus sp. , Ebersole et al., p. 50, fig. 17.
Etymology The species is named in honor of Dennis Parmley, retired faculty member at Georgia College and State University, in recognition of his numerous contributions to our knowledge of the middle Eocene vertebrate faunas of central Georgia.
Hypodigm
SC2013.44.117 (paratype), first upper left anterior tooth ( Fig. 5a–e View Figure 5 ); SC2013.44.119 (paratype), second upper left anterior tooth ( Fig. 5 f–j View Figure 5 ); SC2013.44.122 (paratype), third upper left anterior tooth ( Fig. 5k–o View Figure 5 ); SC2013.44.120 (paratype), left intermediate tooth ( Fig. 5p– t View Figure 5 ); SC2004.34.175 (holotype), first upper left lateral tooth ( Fig. 5u–y View Figure 5 ); SC2013.44.128 (paratype), first lower right anterior tooth ( Fig. 6a–e View Figure 6 ); SC2013.44.130 (paratype), second lower left anterior tooth ( Fig. 6f–j View Figure 6 ); SC2013.44.132 (paratype), third lower right anterior tooth ( Fig. 6k–o View Figure 6 ); SC2004.34.182 (paratype), fourth lower left anterior tooth ( Fig. 6p–t View Figure 6 ); SC2013.44.157 (paratype), first lower left lateral tooth ( Fig. 6u–y View Figure 6 ); SC2004.34.181 (paratype), lower right posterior tooth ( Fig. 6a View Figure 6 –ad).
Referred specimens
SC2004.34.17, second lower left anterior tooth; SC2004.34.18, third upper left anterior tooth; SC2004.34.19, upper left lateral tooth; SC2004.34.20, upper right lateral tooth; SC2004.34.21, first upper right lateral tooth; SC2004.34.22, upper right lateral tooth; SC2004.34.23, first upper right lateral tooth; SC2004.34.24, upper left lateral tooth; SC2004.34.25, lateral teeth (seven specimens); SC2004.34.26, upper lateral teeth (17 specimens); SC2004.34.27, unassigned teeth (two specimens); SC2004.34.28, upper lateral teeth (two specimens); SC2004.34.29, lower lateral tooth; SC2004.34.30, anterior teeth (27 specimens); SC2004.34.31, second upper right anterior tooth; SC2004.34.32, anterior tooth; SC2004.34.33, third upper right anterior tooth; SC2004.34.34, upper anterior teeth (13 specimens); SC2004.34.35, upper left lateral tooth; SC2004.34.36, upper lateral teeth (20 specimens); SC2004.34.37, small anterior teeth (eight specimens); SC2004.34.38, upper right lateral teeth (two specimens); SC2004.34.39, first upper left anterior tooth; SC2004.34.40, first lower anterior teeth (two specimens); SC2004.34.176, second lower left lateral tooth; SC2004.34.177, fourth upper left lateral tooth; SC2004.34.178, second? upper left lateral tooth; SC2004.34.179, third? upper right lateral tooth; SC2004.34.180, seventh? upper right lateral; SC2013.44.78, fourth? lower left anterior tooth; SC2004.34.186, lower lateral teeth (23 specimens); SC2013.44.117, first upper left anterior tooth; SC2013.44.118, first upper anterior teeth (12 specimens); SC2013.44.123, upper left lateral tooth; SC2013.44.124, upper lateral teeth (10 specimens); SC2013.44.125, second upper right lateral tooth; SC2013.44.126, first upper right lateral tooth; SC2013.44.127, first upper right lateral tooth; SC2013.44.129, first lower anterior teeth (two specimens); SC2013.44.131, lower anterior teeth (three specimens); SC2013.44.133, lower right lateral tooth; SC2013.44.134, lower right lateral tooth; SC2013.44.135, lower lateral teeth (20 specimens); SC2013.44.136, anterior teeth (six specimens); SC2013.44.137, third upper anterior teeth (two specimens; SC2013.44.138, incomplete anterolateral teeth (three specimens); SC2013.44.139, upper left lateral teeth (two specimens); SC2013.44.140, lateral teeth (14 specimens); SC2013.44.141, second upper left anterior tooth; SC2013.44.142, pathological tooth; SC2013.44.143, teeth from various jaw positions (229 specimens); SC2013.44.151, ablated teeth from various jaw positions (183 specimens).
Type stratum
Riggins Mill Member, Clinchfield Formation, middle Eocene (Bartonian Stage), calcareous nannofossil zone NP17 ( Fig. 2b View Figure 2 ).
Type locality
Hardie Mine (reclaimed; 32.90027, −83.36499; 32 ◦ 54 Į 1 ĮĮ N, 83 ◦ 21 Į 54 ĮĮ W), near Gordon , Wilkinson County, Georgia, USA ( Fig. 2a View Figure 2 ) GoogleMaps .
Description
First upper anterior teeth. These small teeth, which do not exceed 21 mm in total height, are slightly asymmetrical in labial view ( Fig. 5b View Figure 5 ). The main cusp is very narrow, is slightly distally inclined, and has a sigmoidal profile ( Fig. 5c, d View Figure 5 ). Mesial and distal cutting edges are sharp, smooth, and subparallel but never reach the base of the main cusp. There may be a minuscule tubercle or very short and sharp ridge at the very base of the main cusp, well separated from the main cutting edge ( Fig. 5e View Figure 5 ). A single pair of short, conical cusplets is located at the crown foot ( Fig. 5a View Figure 5 ). The labial face of the main cusp is smooth, is flat apically but weakly convex on its lower half, and in distal view appears to have a slight twist. In contrast, the lingual face is very convex and may bear faint longitudinal ridges on the lower half. The root is bilobate and has a large lingual boss that is bisected by an elongate and deep nutritive groove ( Fig. 5a, c, d View Figure 5 ). The lingual dental band at the crown foot is conspicuous and sometimes deeply impressed. Root lobes are rather short and may be cylindrical or mesiodistally compressed. The distal lobe is more elongated and more obviously angled away from the nutritive groove ( Fig. 5b, c View Figure 5 ).
Second upper anterior teeth. The largest specimen measures 33 mm in total height. The main cusp is tall and narrow, more triangular in appearance than the main cusp of the first anterior tooth, and slightly distally inclined. Cutting edges are biconvex apically but otherwise subparallel ( Fig. 5g, h View Figure 5 ), and they do not reach the cusp base ( Fig. 5j View Figure 5 ). The labial face is smooth and flat to very weakly convex, but the lingual face is very convex and may bear fine vertical ridges on the lower half. The main cusp is flanked by a single pair of cusplets, although a second diminutive cusplet was occasionally observed on the mesial side ( Fig. 5g, h View Figure 5 ). Cusplets are conical to triangular, sharply pointed, and lingually curved. Conical cusplets lack cutting edges, but more triangular cusplets exhibit complete cutting edges. The lingual boss bears a thin nutritive groove, and the dental band may be impressed ( Fig. 5f, h View Figure 5 ). Although root lobes are of nearly the same length, the mesial lobe is labiolingually thick, mesiodistally thin, and pointed basally, whereas the distal lobe is labiolingually thin, mesiodistally wide, and rounded basally ( Fig. 5g, h View Figure 5 ).
Third upper anterior teeth. The largest specimen measures 32 mm in total height. Teeth from this position differ from those of the other anterior positions in having a main cusp that is distally directed, often mesially curving, and only weakly sigmoidal in profile ( Fig. 5l–n View Figure 5 ). In addition, root lobes are asymmetrically developed, with the mesial lobe being much more elongated than the distal one, as well as sharply divergent from the nutritive groove ( Fig. 5l, m View Figure 5 ). The labial face of the main cusp is smooth and very nearly flat, whereas the lingual face is convex and may bear very fine and discontinuous vertical ridges on the lower half. The cutting edges are smooth and sharp and extend to the crown foot ( Fig. 5o View Figure 5 ). The base of the cutting edge may be continuous or denticulated. Lateral cusplets are small but broad, more labiolingually compressed, and with a more conspicuous cutting edge than those of the first two anterior files ( Fig. 5l, m View Figure 5 ). The lingual dental band is conspicuous and may be impressed, and although the nutritive groove is elongated, the boss is less robust than is seen on the other two anterior files ( Fig. 5k, m, n View Figure 5 ).
Intermediate teeth. A single left intermediate tooth is represented. It measures nearly 8 mm in total height and 4 mm in width. The crown consists of a rather short and narrow main cusp that is straight and flat in profile (not sigmoid) and slightly distally inclined ( Fig. 5q–s View Figure 5 ). There is a single pair of lateral cusplets, with the distal cusplet being larger ( Fig. 5q View Figure 5 ). The labial face of the main cusp is flat, whereas the lingual face is very convex, and the cutting edge is continuous from the apex to the lateral cusplets. The root is bilobate with short (the distal lobe is longer), divergent lobes having rounded ends ( Fig. 5r View Figure 5 ). A large lingual boss is bisected by an elongated nutritive groove ( Fig. 5r–t View Figure 5 ).
Upper lateral teeth. Upper lateral teeth can be differentiated from the anterior teeth in that the main cusp is labiolingually thinner, flat, and distally inclined, and the base is broader ( Fig. 5v–x View Figure 5 ). Root lobes are shorter but wider, and they are more strongly divergent. The first few upper lateral tooth files are identified by their more elongated, narrower, and basally pointed mesial lobe, compared to the short, wide, rounded distal lobe ( Fig. 5v, w View Figure 5 ). Other lateral teeth have more equidimensional root lobes and are difficult to place into a specific file. Within our sample of upper lateral teeth, it appears that the crown decreases in size but becomes more strongly distally inclined towards the commissure.
The main cusp of lateral teeth is broad-based but sharply tapering, distally inclined, and straight in profile view. The labial face is smooth and flat to very weakly convex, but the lingual face is convex (although not as strongly as anterior teeth) and may bear fine vertical ridges on the lower half. The cutting edges are smooth and sharp and extend to the very base of the main cusp. The mesial and distal cutting edges may be straight, but more commonly the upper part of the main cusp appears distally curving because the mesial edge is convex and the distal edge straight to concave ( Fig. 5v View Figure 5 ). The base of the cutting edge may be continuous and sharp or sometimes punctuated by one or more rounded-to-pointed denticles ( Fig. 5u View Figure 5 ). The main cusp is usually flanked by a single pair of low, broadly triangular lateral cusplets ( Fig. 5v, w View Figure 5 ), but occasionally a poorly developed second pair was observed ( Fig. 5u View Figure 5 ). The lingual face of each cusplet is more convex than the labial face, and the cutting edge is complete from the mesial to distal side. An elongated and deep lingual nutritive groove divides the root into roughly equidimensional, subrectangular lobes with pointed ends ( Fig. 5w, y View Figure 5 ). The interlobe area is V-shaped, and many teeth have a labiobasal depression at the crown base. The lingual dental band is impressed, but the root boss is less distinctive than on anterior teeth ( Fig. 5y View Figure 5 ). Root width is nearly equal to total tooth height.
Upper posterior teeth. No upper posterior teeth have been identified in the sample.
First lower anterior teeth. Teeth from this file are not known to exceed 13 mm in total height. The main cusp is very narrow and may be straight to weakly curved distally, and it is inclined towards the symphysis ( Fig. 6c, d View Figure 6 ). The labial face is weakly convex and smooth, whereas the lingual face is very convex ( Fig. 6e View Figure 6 ). Cutting edges are smooth, sharp, and subparallel and do not reach the crown foot. A minuscule tubercle or very short and sharp edge, well separated from the main cutting edge, may occur. A single pair of lateral cusplets flanks the main cusp, and in labial view the mesial cusplet appears to be located higher on the tooth than the distal cusplet ( Fig. 6c, d View Figure 6 ). Cusplets are small, conical, sharply pointed, and lingually curving ( Fig. 6a View Figure 6 ). The root is laterally compressed and bilobate with a much shorter mesial lobe, and the large lingual boss is bisected by a nutritive groove ( Fig. 6b–e View Figure 6 ). Root height is equal to crown height.
Second lower anterior teeth. Teeth in this position are symmetrical and reach at least 32 mm in total height. The main cusp is tall, narrow, and erect and has a sigmoidal profile ( Fig. 6h–j View Figure 6 ). The labial face is smooth and flat apically but may be more convex near the base, whereas the lingual face is very convex ( Fig. 6j View Figure 6 ) and may bear fine vertical ridges on the lower half. The cutting edges are subparallel and appear biconvex due to medial curvature near their base, and the edges end well before the cusp base ( Fig. 6h, i View Figure 6 ). A single pair of conical, sharply pointed, and lingually curved lateral cusplets is present ( Fig. 6f View Figure 6 ). The root is bilobate with a large lingual boss that is bisected by a deep nutritive groove, and the dental band is wide and impressed ( Fig. 6g, i, j View Figure 6 ). Root lobes are elongated and of equal length, although the mesial lobe may be slightly wider ( Fig. 6h, i View Figure 6 ). Root height is roughly one-third (30 %) of the total tooth height.
Third lower anterior teeth. These teeth ( Fig. 6k–o View Figure 6 ) are essentially the same as those of the second anterior file. However, they can be distinguished by their more divergent root lobes and an elongated and narrower mesial root lobe compared to the distal lobe ( Fig. 6m, n View Figure 6 ).
Fourth lower anterior teeth. Teeth in this file ( Fig. 6p–t View Figure 6 ) are morphologically similar to those in the third upper anterior file (i.e., Fig. 5k–o View Figure 5 ), but they differ in that the main cusp is distally inclined but not mesially curving and both root lobes are slightly more elongated ( Fig. 6r, s View Figure 6 ). Cutting edges very nearly reach the crown foot. A single pair of lateral cusplets flanks the main cusp, and these cusplets bear conspicuous cutting edges and are broader than those on the more proximal anterior teeth ( Fig. 6p–s View Figure 6 ). The distal root lobe is shorter, wider, and more rounded than the mesial lobe, which is elongated and pointed at the end ( Fig. 6r, s View Figure 6 ). The root lobes of teeth from this file are more divergent than on the third lower anterior file (compare Fig. 6m View Figure 6 to Fig. 6r View Figure 6 ).
Lower lateral teeth. Lower lateral teeth can be differentiated from the anterior teeth in that the crown is shorter, labiolingually thinner, and rather flat and cutting edges extend to the crown foot ( Fig. 6w–y View Figure 6 ). Root lobes are shorter but wider, and they are more widely separated ( Fig. 6x View Figure 6 ). The root lobes in the first few lower lateral files have a slightly shorter and wider mesial lobe compared to the distal lobe, but other lateral teeth have more equidimensional root lobes and are difficult to place into a specific file. Within our sample of lower lateral teeth, it appears that the crown decreases in size and becomes slightly distally inclined towards the commissure. Lower lateral teeth are distinguished from upper lateral teeth by having erect main cusps as opposed to conspicuously distally inclined ones, and root lobes are shorter, lower, and more pointed (compare Fig. 6w View Figure 6 to Fig. 5v View Figure 5 ).
In general, the main cusp is broad-based but sharply tapering, vertical to slightly distally inclined, and virtually flat with little to no lingual curvature. The labial face is smooth and flat to very weakly convex, but the lingual face is convex (although not as strongly as on anterior teeth) and may bear fine vertical ridges on the lower half. The cutting edges are smooth and sharp and extend to the very base of the main cusp ( Fig. 6u View Figure 6 ). The mesial and distal cutting edges are usually straight, but some teeth exhibit a mesial edge that is convex on its upper part. The base of the cutting edge may be smooth and continuous or punctuated by one or more rounded-to-pointed denticles. The main cusp is flanked by a single pair of low, broadly triangular lateral cusplets ( Fig. 6w, v View Figure 6 ), but a poorly developed second pair on one or both sides sometimes occurs. The lingual face of the cusplet is more convex than the labial face, and the cutting edge is complete from the mesial to distal side. An elongated and deep lingual nutritive groove divides the root into low, roughly equidimensional lobes with rounded or pointed ends ( Fig. 6w, x View Figure 6 ). The lingual dental band is impressed, but the root boss is less distinctive than on anterior teeth ( Fig. 6v, y View Figure 6 ). Root width nearly equals total tooth height.
Lower posterior teeth. A single lower posterior tooth measures 5 mm in height and 5.5 mm in width. The crown is very low, broadly triangular, bluntly pointed, and slightly distally directed ( Fig. 6 View Figure 6 ab, ac). There is a single pair of rather large but low, broad, and blunt lateral cusplets ( Fig. 6z View Figure 6 , ac). The labial crown face is flat and bears heavy basal vertical wrinkling. The root is bilobate and bisected by a lingual nutritive groove ( Fig. 6 View Figure 6 aa, ac). Lobes are short, wide, and basally pointed, separated by a V-shaped interlobe area ( Fig. 6 View Figure 6 ab, ac). Posterior teeth having a very low, convex crown that is poorly differentiated from the lateral cusplets, like those occurring near the jaw commissure of extant Carcharias taurus , are unknown for M. parmleyi sp. nov.
Remarks
Mennerotodus parmleyi sp. nov. differs from M. glueckmani (including M. g. glueckmani and M. g. usunbassi) in having anterior teeth that do not exceed 3.5 cm in total height and in lateral teeth generally having only a single pair of lateral cusplets (on rare occasions there is a second diminutive cusplet on one or both sides of the main cusp). In contrast, anterior M. glueckmani teeth can attain 7 cm in total height and lateral teeth have two pairs of mesial and distal cusplets. The lower lateral tooth of M. g. boktensis illustrated by Zhelezko (1994, pl. 6.3) has two pairs of lateral cusplets, and the mesial and distal cusplets of the upper left lateral tooth (pl. 6.4) are broad and appear to be serrated. The crown of M. parmleyi sp. nov. is less curved than that of M. glueckmani usunbassi , and the root lobes are more elongated than on the teeth of both M. g. glueckmani and M. g. usunbassi.
Mennerotodus parmleyi sp. nov. attains a larger overall size than M. mackayi sp. nov. (i.e., anterior teeth reach 3.3 cm in height vs. 2.4 cm). When present, denticulation on M. parmleyi sp. nov. is more conspicuous and more extensively developed than on M. mackayi sp. nov. In addition, upper lateral teeth of M. parmleyi sp. nov. are as wide (root width) as they are tall (total tooth height), whereas equivalent teeth of M. mackayi sp. nov. are taller than they are wide. Also, lingual faces of M. parmleyi sp. nov. teeth may bear fine longitudinal ridges, but crown enameloid of M. mackayi sp. nov. is generally smooth. In nearly all tooth positions, the ratio of crown height to root height is greater on M. parmleyi sp. nov. teeth than on M. mackayi sp. nov.
The upper lateral Mennerotodus sp. tooth illustrated by Dutheil et al. (2006, pl. 2.3) differs from all available M. parmleyi sp. nov. upper lateral teeth in that the mesial cusplet is serrated, as opposed to denticulation occurring at the base of the main cusp (medial to the cusplet).
In their report on the fossil sharks from the Clinchfield Formation in central Georgia, Parmley and Cicimurri (2003) reported several Carcharias -like tooth morphologies that they identified as Carcharias acutissimus , C. hopei (= Hypotodus verticalis ; Agassiz, 1843), C. koerti (= Brachycarcharias koerti ; Stromer, 1910), and Striatolamia cf. macrota ( Agassiz, 1843) . The lateral teeth they identified as C. koerti are distinctive for their large size, broadly triangular main cusp, and two pairs of robust and diverging lateral cusplets. We believe that this morphology is more appropriately identified as Brachycarcharias twiggsensis ( Case, 1981) , and this taxon will not be confused with Mennerotodus parmleyi sp. nov. (also Ebersole et al., 2019).
Of the three remaining taxa, Parmley and Cicimurri (2003) differentiated Carcharias acutissimus from C. hopei based primarily on the presence or absence of lingual crown ornamentation. However, our examination of two C. taurus dentitions (SC86.62.6 and SC2000.120.6) showed that these features are variable and may not be taxonomically significant (also Applegate 1965; Purdy et al., 2001). Our evaluation of the Clinchfield Formation odontaspidid teeth leads us to conclude that the material identified as C. acutissima and C. hopei by Parmley and Cicimurri (2003) is conspecific and represents variation within Mennerotodus parmleyi sp. nov. This is corroborated by the fact that those authors noted (p. 161) that some of their C. hopei lateral teeth exhibited “serrations” between the cusplets and main cusp.
Parmley and Cicimurri (2003) described their Striatolamia cf. macrota tooth as having lingual crown ornamentation and cutting edges extending to the crown foot. Based on our reconstruction of the Mennerotodus parmleyi sp. nov. dentition, this tooth represents a very large (adult) M. parmleyi sp. nov. distally located anterior tooth. Anterior teeth of Striatolamia macrota that we examined in large samples from the Bartonian Tupelo Bay Formation of South Carolina (at SC) and Gosport Sand of Alabama (at MSC) show that the lingual crown ornamentation is very robust and extends to at least two-thirds of the crown height, and lateral cusplets are diminutive. Additionally, when compared to M. parmleyi sp. nov., lateral teeth of S. macrota have a broader crown with a less pointed apex, lateral cusplets (single pair) are broader and rounded (the distal cusplet being larger than the mesial one), and root lobes are shorter but broader. The single intermediate tooth we attribute to M. parmleyi sp. nov. is identical to intermediate teeth occurring on the upper jaws of the two C. taurus dentitions we examined (SC86.62.6 and SC2000.120.6). Of the two other lamniform sharks occurring within the Clinchfield Formation, the teeth of Macrorhizodus praecursor lack lateral cusplets and the teeth of Brachycarcharias twiggsensis are larger in overall size, have much broader crowns, and have much larger lateral cusplets ( Case, 1981).
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