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Symphyseal tooth of Edestus minor , TMM 46034-1. (A) Distal (side facing away from the midline) view. Side of base with hollow groove is above. Lingual edge of crown is above; labial edge is below. Note truncated apex. Scale bar = 5 cm. (B) Abraded surface of apex. Scale bar = 1 cm.
Source publication
The paired symphyseal tooth whorls of the Carboniferous chondrichthyan Edestus are perhaps the most enigmatic dental structures of any known vertebrate. The tooth whorls have been compared to scissors or to saw blades. It is commonly held that the tooth whorls were used in opposition, to cut prey caught between them. However, the curvature of the w...
Contexts in source publication
Context 1
... holotype of E. minor is a single, isolated tooth, AMNH FF477, since it is the sole specimen upon which the original description by Newberry (1866) was based. A tooth whorl containing seven teeth, ACM 85, was described and figured by Hitchcock (1856), but not named by him. That specimen was later referred to E. minor by Newberry (1889, pl. 39, fig. 1), and has been treated by some as if it were the holotype (Itano 2014b). For a recent depiction of ACM 85, see (Itano 2014a, fig. 3B). While the crowns of ACM 85 resemble those of E. minor, there are also some differences. The serrated edges of the crown of E. minor taper continuously to the apex. The edges of the crowns of ACM 85 taper slowly near the base and more rapidly near the apex. Specimen USNM V7255 (Fig. 1) was designated as the holotype of a new species, Edestus mirus Hay, 1912, because the crowns differed from those of ACM 85 (Hay 1912), ignoring the fact that they are not distinguishable from the crown of AMNH FF477. Thus, E. mirus should be considered to be a junior synonym of E. minor, since USNM V7255 displays no characters to distinguish it from AMNH FF477. It might prove necessary to refer ACM 85 to a species other than E. minor, but the range of variation within E. minor should be investigated before making such a ...
Context 2
... TMM 46034-1 has a truncated apex (Fig. 3A). The exposed surface on the remaining part of the tooth is smooth and convex (Fig. 3B). The smooth surface is presumably a result of abrasion during life. Given what is known of the morphology of the tooth whorls (e.g., from Fig. 1), it is difficult to imagine how the wear could have resulted from contact with an opposing dentition. More likely, part of the apical tip was broken off, perhaps as a result of striking a hard object, leaving the internal dentine of the crown exposed. Subsequent, repeated contact with prey having an abrasive outer covering, such as skin covered with thick scales (e.g., palaeoniscoid fish) or dermal denticles (e.g., chondrichthyans) might have resulted in the observed smooth surface. It seems unlikely that the wear could have occurred postmortem, given the good preservation of the rest of the tooth, particularly the surface of the crown. The large extent of the wear seems to indicate slow tooth replacement compared to that in extant sharks. The orientation of the abraded surface indicates motion of the tooth perpendicular to its basal-apical axis, most likely in the vertical plane (since the serrated edges would be most effective in that case), in order to disable prey by cutting them. This action might have been carried out by moving the anterior part of the body up and down, probably with jaws fixed relative to each other. Such a mode of predation does not seem to have been reported in any other organism, either extinct or extant. conTrasT WiTh TooTh Wear in Helicampodus Figure 4 shows a symphyseal tooth whorl of another edestoid, Helicampodus kokeni Branson, 1935, from the Permian of Pakistan. Due to the limited fossil record of Helicampodus, there is no way to know whether this represents an upper or lower tooth whorl and whether one or two such tooth whorls were present. What can be observed are planar wear facets on several of the crowns. The facets were noted by Branson (1935). In Fig. 4 the facets are enhanced by observation in reflected light. The facet on the second crown from the left in Fig. 4 is the best preserved. The facet on the third crown from the left ...
Context 3
... TMM 46034-1 has a truncated apex (Fig. 3A). The exposed surface on the remaining part of the tooth is smooth and convex (Fig. 3B). The smooth surface is presumably a result of abrasion during life. Given what is known of the morphology of the tooth whorls (e.g., from Fig. 1), it is difficult to imagine how the wear could have resulted from contact with an opposing dentition. More likely, part of the apical tip was broken off, perhaps as a result of striking a hard object, leaving the internal dentine of the crown exposed. Subsequent, repeated contact with prey having an abrasive outer covering, such as skin covered with thick scales (e.g., palaeoniscoid fish) or dermal denticles (e.g., chondrichthyans) might have resulted in the observed smooth surface. It seems unlikely that the wear could have occurred postmortem, given the good preservation of the rest of the tooth, particularly the surface of the crown. The large extent of the wear seems to indicate slow tooth replacement compared to that in extant sharks. The orientation of the abraded surface indicates motion of the tooth perpendicular to its basal-apical axis, most likely in the vertical plane (since the serrated edges would be most effective in that case), in order to disable prey by cutting them. This action might have been carried out by moving the anterior part of the body up and down, probably with jaws fixed relative to each other. Such a mode of predation does not seem to have been reported in any other organism, either extinct or extant. conTrasT WiTh TooTh Wear in Helicampodus Figure 4 shows a symphyseal tooth whorl of another edestoid, Helicampodus kokeni Branson, 1935, from the Permian of Pakistan. Due to the limited fossil record of Helicampodus, there is no way to know whether this represents an upper or lower tooth whorl and whether one or two such tooth whorls were present. What can be observed are planar wear facets on several of the crowns. The facets were noted by Branson (1935). In Fig. 4 the facets are enhanced by observation in reflected light. The facet on the second crown from the left in Fig. 4 is the best preserved. The facet on the third crown from the left ...
Citations
... It is useful to compare and contrast the tooth wear observed in Karpinskiprion to that observed in Edestodus (Itano 2015) and Edestus (Itano 2018). These latter two closely related genera are known to possess symphyseal tooth whorls of similar size in both jaws. ...
Restudy of Campyloprion annectans Eastman, 1902 from North America demonstrated that neither specimen included is diagnostic at the species level; thus, the species name is a nomen dubium. Since this species was designated as the type species of the genus, this requires suppression of the generic name also. Another species earlier assigned to Campyloprion, Campyloprion ivanovi Karpinsky,
1924 is used as a type for a newly established genus Karpinskiprion Lebedev et Itano gen. nov. The composition of the family Helicoprionidae Karpinsky, 1911 is reviewed, and a new family Helicampodontidae Itano et Lebedev fam. nov. is erected.Anew specimen of Karpinskiprion ivanovi (Karpinsky, 1924) recently discovered in the Volgograd Region of Russia is the most complete Karpinskiprion specimen ever found. It unambiguously demonstrates the coiled nature of these tooth whorls and presents information on their developmental stages. During organogeny, cutting blades of the crown became reshaped, and basal spurs progressively elongated, forming a grater.Whorl growth occurred by addition of new crowns to the earlier mineralised base followed by later spur growth. In contrast to consistently uniform cutting blades, spurs are often malformed and bear traces of growth interruption. Both sides of the outer coil of the tooth whorl bear lifetime wear facets. The youngest (lingual) crowns are as yetunaffected by wear. The best-preserved facets show parallel radially directed scratch marks. The upper jaw dentition of Karpinskiprion is unknown, but we suggest that the faceted areas resulted from interaction with the antagonistic dental structures here. Three possible hypotheses for this interaction are suggested: (a) two opposing whorls acted as scissor blades, moving alternately from one side to another; (b) the lower tooth whorl fitted between paired parasymphyseal tooth whorls of the opposing jaw; or (c) the lower tooth whorl fitted into a dental pavement in the upper jaw.
... Furthermore, extrapolating the anatomy and joints of the E. heinrichi jaw to the other three species is regarded here as reasonable, with some consideration. The asymmetric species E. triserratus and E. minor have whorls that exhibit a greater degree of curvature, leading Itano [8,38,39,40] to imagine the whorls to curl outside the mouth for a vertical slashing motion. The evidence used for this hypothesis include several specimens of Edestus teeth showing wear patterns that are predominantly transverse to the crown (i.e., parallel to the base) [38,39,40]. ...
... The asymmetric species E. triserratus and E. minor have whorls that exhibit a greater degree of curvature, leading Itano [8,38,39,40] to imagine the whorls to curl outside the mouth for a vertical slashing motion. The evidence used for this hypothesis include several specimens of Edestus teeth showing wear patterns that are predominantly transverse to the crown (i.e., parallel to the base) [38,39,40]. This wear pattern is entirely consistent with the anatomy and functional reconstruction of FMNH PF 2204 [2], showing that Edestus whorls were positioned in opposition inside the mouth, and that the biting motion involved anterior-posterior slicing with the lower whorl. ...
This study reevaluates the tooth morphology used to define species within the genus Edestus (Chondrichthyes, Euchondrocephali). Known as the scissor tooth shark, Edestus produced a unique dentition of spiraled tooth families positioned in the symphysis (midline) of the upper and lower jaws. Morphometric analysis of more than 200 ejected teeth and intact spiral tooth whorls demonstrates that teeth from the upper and lower whorls differ in shape and ontogeny. Comparison of these data to the type specimens of 13 existing species reduces the number of morphologically distinct Edestus to just four species and refines the stratigraphic occurrence and expansion of the group. E. triserratus has a narrow bullet-shaped crown that points anteriorly and has roots of intermediate length. E. minor crowns have a wider triangular base, whereas the crowns of E. heinrichi form nearly equilateral triangles and are supported by an elongated root. E. vorax, which also has roughly equilateral triangular crowns, has short and deep roots, and is only known from very large specimens that are distinct from the growth series of E. heinrichi. Tooth and whorl morphologies among the species are consistent with cranial anatomy observed in a juvenile E. heinrichi and with transverse tooth-wear patterns to suggest Edestus used a forward to backward slicing motion to bite its prey. Extrapolating body size from tooth whorl length provides a conservative estimate that E. heinrichi could exceed 6.7 m in length. Edestus fossils are recovered from coastal marine to estuarine deposits spanning roughly six million years (313-307 Ma). Edestus first appears in England during the latest Bashkirian (313 Ma, Carboniferous), a few million years after its most closely resembling genus Lestrodus. Diversification and range expansion of Edestus coincides with the Moscovian transgression that flooded Laurentia and the Russian platform.
... Macrowear sustained during life has been reported on a tooth of E. minor from the Smithwick Shale (Pennsylvanian, late Atokan = Moscovian) of San Saba County, Texas, USA (Itano, 2015). The apex of the crown is truncated, and the surface of the remaining part is smooth and convex, as if worn by repeated contact with an abrasive surface, such as the skin of a large fish covered with scales or denticles. ...
... Many of the teeth in the sample were considered not useful for this study because the apical parts of the crown were truncated (broken off). In none of the cases in which the crowns were apically truncated was the surface of the remaining part of the crown smoothly polished, as for the Edestus minor tooth described by Itano (2015). Others, e.g., TMM 40234-18 (Figure 4.4), have had much of the outer, hypermineralized layer removed. ...
The symphyseal tooth whorls of the Carboniferous chondrichthyan Edestus consist
of files of teeth having sharply-pointed, serrated crowns, joined at their bases. A single tooth whorl was present in each jaw. How these tooth whorls functioned is unclear, since their convex curvature allows only a few of the most lingual crowns of opposing tooth whorls to occlude. Rather than working in opposition, like scissors, the more labial teeth might have been used to cut and disable prey with a vertical motion of the anterior part of the body. Provided the scratches observed on the surface of Edestus teeth can be inferred to have been generated in the process of feeding, their orientation might be used to distinguish whether the teeth were used mainly in occlusion, to cut prey trapped between the jaws, or mainly to cut prey situated outside the oral cavity. Edestus minor teeth having unusually good surface preservation were examined for microwear. The teeth are from the Strawn Group (Desmoinesian, Middle Pennsylvanian) of San Saba County, Texas, USA. The best-preserved crown surfaces display scratches 50 to 500 micrometers long. The scratches are oriented predominantly transversely to the basal-apical axis. This observation appears to support the vertical slashing hypothesis. However, the possibility that interaction with the substrate contributed to the observed wear cannot be discounted.
... Dozens of blades and hundreds of ejected Edestus teeth have been collected from Pennsylvanian age (330 million years ago) marine shale deposits of midwestern United States and Britain, but cranial material is exceedingly rare. In the absence of anatomical context, functional models of Edestus propose comparisons to slashing sawfish rostrums (Eastman, 1902;Hay, 1909), shearing scissor jaws (Peyer, 1968;Zangerl and Jeremiah, 2004), or fixed vertical slashing weapons (Itano, 2014(Itano, , 2015(Itano, , 2018. Hay (1912) described a specimen of Edestus mirus having blades positioned at the jaw symphysis, though only cartilages at the anteriormost site of attachment were preserved. ...
... (1) loose attachment of the blades to the jaw and shearing passage of opposing blades (scissor: Zangerl and Jeremiah, 2004); (2) large rotations of fixed jaw joints (vertical slashing: Itano, 2014Itano, , 2015Itano, , 2018; or (3) greatly protruding blades (sawfish : Eastman, 1902). In stark contrast to previous depictions of Edestus, the tooth blades curve inward toward the throat presenting an externally streamlined profile of the jaws (Fig. 1B). ...
Sharks of Late Paleozoic oceans evolved unique dentitions for catching and eating soft bodied prey. A diverse but poorly preserved clade, edestoids are noted for developing biting teeth at the midline of their jaws. Helicoprion has a continuously growing root to accommodate more than 100 crowns that spiraled on top of one another to form a symphyseal whorl supported and laterally braced within the lower jaw. Reconstruction of jaw mechanics shows that individual serrated crowns grasped, sliced, and pulled prey items into the esophagus. A new description and interpretation of Edestus provides insight into the anatomy and functional morphology of another specialized edestoid. Edestus has opposing curved blades of teeth that are segmented and shed with growth of the animal. Set on a long jaw the lower blade closes with a posterior motion, effectively slicing prey across multiple opposing serrated crowns. Further examples of symphyseal whorls among Edestoidae are provided from previously undescribed North American examples of Toxoprion, Campyloprion, Agassizodus, and Sinohelicoprion. The symphyseal dentition in edestoids is associated with a rigid jaw suspension and may have arisen in response to an increase in pelagic cephalopod prey during the Late Paleozoic.
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... An isolated tooth of Edestus minor with a truncated, smoothly worn apex was reported recently (Itano 2015a). The wear was hypothesized to be caused by contact with the skin of large prey having skin covered with hard denticles or scales. ...
... 2) The individual was injured so that it was unable to feed on mobile prey and was forced to feed on prey, dead or alive, that was immobile or poorly mobile. The wear observed on a tooth of Edestus minor (Itano 2015a) might have resulted from a similar set of circumstances. ...
Edestus is a Middle Pennsylvanian chondrichthyan possessing symphyseal tooth whorls in both the upper and lower jaws. The curvature of the tooth whorls prevents most of the crowns of the opposing whorls from occluding with each other. For that reason, it has recently been hypothesized that the tooth whorls were used to slash prey with a vertical motion of the anterior part of the body, not to cut prey caught between them. A tooth of Edestus minor having a truncated, smoothly worn apex has been reported previously. Here, a partial tooth whorl of a different species, Edestus heinrichi, is described. The apices of the crowns are worn, so that the crown heights are reduced by about one third. The more labial (older) of the two preserved crowns shows more wear than the more lingual (younger) one. In contrast to the previously reported E. minor tooth, wear is observed to the serrations as well as to the apices of the crowns. The observed wear on both the E. minor tooth and on the E. heinrichi tooth whorl supports the recent hypothesis on the function of the tooth whorls. In both cases, the apices might have been abraded by attempted predation on or scavenging of large fish having skin covered with denticles or scales.
... It is possible that the tooth whorl fits entirely inside the oral cavity, as is the case for Sarcoprion (Nielsen 1952). It is also possible that the labial end of the tooth whorl extended outside the oral cavity, as has been hypothesized for Edestus (Itano 2014(Itano , 2015(Itano , 2018. ...
Campyloprion Eastman, 1902 is a chondrichthyan having an arched symphyseal tooth whorl similar to that of Helicoprion Karpinsky, 1899, but less tightly coiled. The holotype of Campyloprion annectans Eastman, 1902, the type species of Campyloprion, is of unknown provenance, but is presumed to be from the Pennsylvanian of North America. Campyloprion ivanovi (Karpinsky, 1922) has been described from the Gzhelian of Russia. A partial symphyseal tooth whorl, designated as Campyloprion cf. C. ivanovi, is reported from the Missourian Tinajas Member of the Atrasado Formation of Socorro County, New Mexico, USA. Partial tooth whorls from the Virgilian Finis Shale and Jacksboro Limestone Members of the Graham Formation of northern Texas, USA, are designated as Campyloprion sp. Two partial tooth whorls from the Gzhelian of Russia that were previously referred to C. ivanovi are designated as Campyloprion cf. C. annectans. The age of Toxoprion lecontei (Dean, 1898), from Nevada, USA, is corrected from the Carboniferous to the early Permian. An alternative interpretation of the holotype of T. lecontei is presented, resulting in a reversal of its anterior-to-posterior orientation. The genera Helicoprion, Campyloprion, and Shaktauites Tchuvashov, 2001 can be distinguished by their different spiral angles.
