Zonneveld et al.—Bored turtle shell
K. lakkos in its cylindrical versus hemispherical morphology and from K. fiale in its straight walls and lack of complete penetration. Karethraichnus kulindros are overall much rarer than K. fiale and approximately as common as K. fiale.
Karethraichnus fiale new ichnospecies
Diagnosis.—Penetrative Karethraichnus having a cylindrical to bi-convex or flask-shaped profile, axis approximately perpen- dicular to the substrate surface.
Description.—Karethraichnus fiale penetrate fully through individual shell elements (Figs. 7.1–7.4, 7.9–7.11). Where they penetrate through thick cortical bone and minimal trabecular (cancellous) bone, the shaft of this trace is typically straight and is oriented approximately perpendicular to the shell surface (Fig 8.2). In-shell elements with thin cortical bone and a thicker cancellous bone layer these trace are typically biconvex, with the thickest portion of the trace occurring in the center of the bone (Fig. 8.2).
Etymology.—From the greek ‘fiale’ (romanization of φιάλη) meaning flask, referring to the bi-convex shape of the traces.
Types.—The holotype (UA-TF148-1) consists of a circular bi-convex hole through the medial portion of a costal bone (Fig. 7.1, 7.2, and 7.9). Paratypes are designated as other penetrative holes on the same specimen (Figs 7.3, 7.4; 7.9– 7.11), including a penetrative hole capped by a hemispherical bone patch (Fig. 7.6–7.8) The type locality consists of badland hills below Continental Peak, consisting of interstratified ped- ogenically altered siltstone and mudstone, and sheet-like to channelized sandstone and conglomerate of the Cathedral Bluffs Tongue of the Wasatch Formation in the Honeycomb Buttes area, South Pass, Wyoming (Fig. 1.2).
Occurrence.—Early Eocene, Cathedral Bluffs Tongue, Wasatch Formation, South Pass, Wyoming.
Remarks.—The clavate or flask-shape of trace fossils such as Teredolites in woodground substrates and Gastrochaenolites in hardground settings reflects the gradual, in situ growth of the trace maker (Kelly and Bromley, 1984). In contrast, the flask shape of K. fiale is interpreted to reflect penetration through several different bone types, including the hard, dense external and internal cortex bone and the softer, more coelous internal trabecular bone (Fig. 5). Many, although not all, Karethraichnus fiale are character- ized by a raised lip, bone spur, or bone patch that may narrow, or
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completely cover the hole. This bone growth is not considered a diagnostic component of the ichnospecies. This ichnospecies differs from K. kulindros in their biconvex morphology and penetration depths that equals or (in examples with secondary bony healings or patches) exceeds the primary thickness of the bone. Karethraichnus fiale represents a breach through the external bone armor of the host organism. The bone growth indicates that, despite the presence of the parasite, negative affects to the host taxon were insufficient to kill it immediately (if at all).
Ichnogenus Thatchtelithichnus new ichnogenus
Type ichnospecies.—Thatchtelithichnus holmani new ichnospecies.
Other ichnospecies.—Thatchtelithichnus bagginsi new ichnospecies.
Diagnosis.—Circular to subcircular grooves with a central boss or platform, bored into a bone substrate. Grooves penetrate into the cortical layer of the bone. The central platform may consist of an unmodified platform or a rounded nubbin. Burrow walls rounded, convex. or sharp and perpendicular to the external substrate surface.
Etymology.—From the greek ‘thachtelithi’ (latinization of
δαχτυλίδι) meaning ‘ring,’ referring to the shape of the speci- men and ‘ichnus’ meaning trace. Occurrence.—Eocene of the Green River Basin, Wyoming.
Remarks.—Thatchtelithichnus bears morphological and size similarities to the ichnogenus Oichnus Bromley, specifically to the taxon Oichnus excavatus Donovan and Jagt, 2002, which occurs in marine and freshwater invertebrates. Recent taxo- nomic reassessments have suggested that Oichnus is a junior synonym of Sedilichnus (Zonneveld and Gingras, 2014). Thatchtelithichnus differs in the nature of the substrate in which the trace occurs (discussed above). Only a single species of Thatchtelithichnus is identified.
Similar to Oichnus excavatus, Thatchtelithichnus ranges in morphology between end-members in which the central platform remains unmodified by the tracemaker and those in which it is modified. Because only a single specimen with an unmodified central platform was identified in the study material, at this time the two morphotypes are included within a single ichnogenus.
Thatchtelithichnus holmani new ichnospecies
Figure 6. Karethraichnus on cf. Echmatemys sp. bones. All scale bars are 5mm. (1–7) Karethraichnus lakkos on the ventral surface of peripherals from a single turtle specimen (UA-TF140). The holotype of K. lakkos (UA-TF140-1) is identified by an arrow in (1). Note the variability in size of individual borings on this single turtle specimen. (8) Karethraichnus lakkos on the dorsal surface of the margin of a right epiplastron (UA-TF141). (9) Solitary K. kulindros on the dorsal surface of a peripheral (UM1032831). (J) Two touching K. kulindros on the dorsal surface of a hyoplastron fragment (UA-TF142). (11) Several K. kulindros and two K. lakkos on a costal fragment, likely of a C3, C4 or a C5 (UA-TF143). (12) Abundant K. lakkos on a hypoplastron fragment (UM102792). Note that the borings follow the edge of the epidermal suture line, a natural access point to the shell through the epidermal layer. (13) The holotype of the deeply penetrating trace fossil K. kulindros on the dorsal surface of a central costal bone (UA-TF140-8). (14, 15) Vertical sections through the holotype of K. kulindros. Note that the boring nearly penetrates through the entire bone and that, although slightly curved, is overall cylindrical. (16) A highly bored costal fragment covered in abundant K. lakkos (UA-TF144). (17, 18). Bored xiphiplastra from the same specimen (UM103361). Note that the borings occur on the ventral surface of the periphery of the bone. S. Single K. lakkos on the dorsal surface of a central costal (UA-TF145). (20, 21) Highly bored plastron fragments with abundant K. kulindros (UA-TF146 and UA-TF147).
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