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Sullivan, R.M. and Lucas, S.G., eds., 2015, Fossil Record 4. New Mexico Museum of Natural History and Science Bulletin 67.

CRETACEOUS TURTLES OF NEW MEXICO

ASHER J. LICHTIG and SPENCER G. LUCAS

New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104-email: ajlichtig@gmail.com

Abstract—Fragments of turtle shell are known from several Cretaceous formations in New Mexico, including the Mancos Shale, Tres Hermanos Formation, Crevasse Canyon Formation, Point Lookout Sandstone, Menefee Formation, Pierre Shale, Ringbone Formation, Fruitland Formation, Kirtland Formation, Ojo Alamo Formation and McRae Formation. Of these, the Tres Hermanos Formation, Mancos Formation, Point Lookout Sandstone, Dalton Member of the Crevasse Canyon Formation and Ringbone Formation have only yielded remains of trionychids. This is largely because most of these units are shoreline sandstones of the Western Interior seaway that contain extensive shark-tooth assemblages with a mixture of a few fragmentary freshwater vertebrate fossils, including those of trionychids. The more terrestrial units of the Crevasse Canyon, Menefee, Fruitland, Kirtland and Ojo Alamo formations yield a more diverse array of fossil turtles, generally consisting of trionychids, baenids and adocids. Among the baenid turtles is the oldest reported record of Denazinemys and an indeterminate bothremydid turtle from the Menefee Formation. In addition to these, the Menefee Formation also yields the first known specimen of Naomichelys from the Cretaceous of New Mexico. The Pierre Shale yields one fossil turtle species, the marine turtle Archelon sp. Further exploration of the Cretaceous strata of New Mexico, especially the Crevasse Canyon and Menefee formations, should yield a much more extensive record of fossil turtles.

INTRODUCTION Hay (1908) and Gilmore (1916) first published on specimens of Cretaceous fossil turtles from New Mexico. These were from the Upper Campanian-Maastrichtian strata (Fruitland, Kirtland and Ojo Alamo formations) of the San Juan Basin (Figs. 1-2). Subsequently, collecting uncovered many more Cretaceous turtles in the San Juan Basin, making it one of the most well studied records of Late Cretaceous turtles in

the North American Western Interior (e.g., Hay, 1908; Gilmore, 1916, 1935; Wiman, 1933; Mateer, 1981; Gaffney et al., 2006; Lucas and Sullivan, 2006; Sullivan et al. 2012). Furthermore, many fossils (mostly fragments) of turtles have been found in Cretaceous formations of New Mexico outside of the San Juan Basin (Figs. 1-2). This paper is a review of the taxonomy and distribution of these fossil turtle specimens. Turtles have been found in the Mancos Formation, Tres Hermanos Formation, Crevasse Canyon Formation, Point Lookout Sandstone, Menefee Formation, Pierre Shale, Ringbone Formation, and McRae Formation. The most abundant remains are from the Menefee and the Crevasse Canyon formations, which thus far yield the most diverse Cretaceous turtle assemblages of New Mexico outside of the Upper Campanian-Maastrichtian strata of the San Juan Basin. Institutional Abbreviations: NMMNH, New Mexico Museum of Natural History and Science, Albuquerque, NM. CHCU, Chaco Culture National Historical Park. USNM, National Museum of Natural History, Washington, DC.

MANCOS FORMATION Collections from the El Vado Member of this marine unit include one trionychid turtle specimen, NMMNH P-51615 (Fig. 3). This specimen consists of three fragments of costal bones, from locality NMMNH L-5499, 20 m above the base of the El Vado Member. Each of these has a surface sculpture of pits similar to those typically found on trionychid shell bones (Scheyer et al. , 2007). The largest of these three costal fragments has a flattened rib on the lower surface.

TRES HERMANOS FORMATION Three turtle specimens have been found in rocks of the Tres Hermanos Formation. These are from locality NMMNH L-5153 and were previously discussed by Spielmann et al. (2009). Of these, one is a dermatemydid and the other two are indeterminate to family. The dermatemydid bone (Fig. 4A-B) is a small piece of bone ~10 mm diameter that has been weathered to a near round shape with the ridges of the ornamentation worn down slightly. The other specimens have a smooth to slightly striated surface sculpture. The larger of the two smooth-shelled specimens, NMMNH P-58067 (Fig. 4C-D), is from the proximal end of a costal bone and has been weathered to a rounded, ~20 mm diameter shape. Three sulci running from the edges of the fragment meet at a point just above where the rib enters the costal bone. This specimen was suggested to be a probable baenid by Spielmann et al. (2009) because of the relatively smooth surface commonly associated with Cretaceous baenids in this region. This is tentatively agreed with for lack of other known families with similar features in the area. The second of these specimens (Fig. 4E-F) consist of seven small carapace fragments, some of which appear to include the full width of costal bones only ~10 mm long, indicating they came from an extremely small, possibly juvenile, turtle.

FIGURE 1. Map of Cretaceous outcrops in New Mexico showing major turtle fossil areas (by county) in New Mexico: 1, San Juan County, Fruitland, Kirtland and Ojo Alamo (Naashoibito Member) formations (late Campanian-Maastrichtian; 2, Sandoval County, Mancos Shale (Juana Lopez Member) (Turonian); 3, Bernalillo County, Point Lookout Sandstone (Santonian); 4, Socorro County, Atarque Sandstone (Turonian); 5, Sierra County, McRae Formation (Hall Lake Member) (Maastrichtian); and 6, Grant and Hidalgo counties, Ringbone Formation (Campanian).

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FIGURE 2. Cretaceous stratigraphic column shows the fossil-turtle-bearing formations of New Mexico. Stratigraphic ranges of turtle taxa shown in the right column.

FIGURE 4. Testudines from the Tres Hermanos Formation A-B- indeterminate trionychid (NMMNH P-58068), A, dorsal view; B-ventral view; C-F, indeterminate testudines (NMMNH P-58067, P-58432); C, E, dorsal views; and D, F, ventral views. Scale bar = 2 cm.

FIGURE 3. Indeterminate trionychids from the Mancos Shale NMMNH P-51615. (left) dorsal view, and (right) ventral view. Scale bar = 2 cm.

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CREVASSE CANYON FORMATION Turtle specimens from this formation include 30 small carapace and plastron fragments as well as a recently discovered partial Adocus shell. Lucas et al. (1988) stated that this formation contains indeterminate trionychid turtle fragments, and until recently, these were the only turtles known from the Crevasse Canyon Formation. Of these, 29 represent indeterminate trionychid fragments and one is a peripheral, likely from a baenid turtle based on the smooth surface. These fragments come from three specimens: NMMNH P-58411, P-28832, and P-28840. In addition to this, NMMNH P-42687 (Fig. 6) from the Dalton Member of the Crevasse Canyon Formation is a complete left second costal from an indeterminate trionychid turtle (Meylan, 1987). This costal is approximately 70 mm wide with a rib projecting an additional 15 mm from the lateral edge. As with NMMNH P-25053 from the Menefee Formation (see below), the outer ~5 mm are smooth, coming to a rounded lateral edge. The remainder of this bone is covered by a typical trionychid pattern of pitting. Recently, carapace and plastron fragments attributable to the genus Adocus (NMMNH P-70008, Fig. 7) were recovered from the Crevasse Canyon Formation in Sierra County (Fig. 1). Identification is based on the shape of the cervical scute and the left auxiliary buttress (see Sullivan et al., 2012). The cervical scute is similar to that of Adocus bossi (USNM 8613), which has a trapezoidal shape, with the narrow, ~10 mm wide end at the anterior lip of the carapace. This scute, as well as the neighboring peripherals, are ~25 mm from the lateral edge to the suture joining the first costals. The ventral surface has a 10 mm lip along the anterior edge, widening laterally to 20 mm. The right auxiliary buttress is similar in shape to that of A. bossi and has similarly placed sulci, suggesting a possible close relationship. Adding further support to placement in the genus Adocus is the upward curving peripherals associated with this specimen. These characteristics are similar to those seen on A. kirtlandicus and A. bossi (Sullivan et al., 2012). Further, the surface sculpture seen on specimens of Adocus from the San Juan Basin is very similar to that present on these fragments. The specimens recovered from the coastal sandstone of the Dalton Member are almost entirely trionychids. These are almost all small unassociated fragments, the exception being the complete costal in Figure 5 (NMMNH P-42687). Conversely, the partial Adocus carapace and plastron (NMMNH P-70008) comes from green shale, coastal

floodplain deposits in an unnamed member that is stratigraphically higher in the Crevasse Canyon Formation.

POINT LOOKOUT SANDSTONE Turtle specimens from this formation include 27 indeterminate trionychid shell fragments. Most of these are small, measuring less than 30 mm along their longest axes. The two largest are costal fragments with a pattern of pitting that becomes more circular toward the sutures of the neighboring bones and more elongate near the center of the bone (Fig. 5A-B). Other fragments show a more ridged pattern with the pits oriented parallel to the short axis of the costal fragment (Fig. 5C). A few trionychid specimens from the Point Lookout Sandstone were briefly discussed in Lucas et al. (1988). Additionally, a single fragment of smooth-surfaced neural bone, NMMNH P-28848 from locality NMMNH L-297, has been found. This neural measures 17 mm long by 19 mm wide and is likely a baenid turtle as no other family with an unsculptured shell has been found in rocks of the same age in the region.

MENEFEE FORMATION The Menefee Formation is a dominantly terrestrial formation, which contains a wide variety of incomplete turtle fossils, including remains of adocids, trionychids, baenids, bothremydids, and the solemydid turtle Naomichelys (NMMNH P-42161: Fig. 8C). These turtles have been found in the Allison and Cleary Coal members. Hunt and Lucas (1993) stated that indeterminate trionychid and baenid carapace and plastron fragments had been found at 13 localities in the Menefee Formation, and two of these were illustrated. Adocid fragments (Fig. 8A) in this area are similar in appearance to the Adocus fragments found in the upper Campanian units of the San Juan Basin (Sullivan et al., 2012). They possess a surface sculpture and a right inguinal buttress similar to NMMNH P-25051, which conforms to that of the holotype specimen of Adocus bossi (USNM 8613: Sullivan et al. 2012). An additional specimen with surface sculpture similar to that seen on adocids (NMMNH P-70338) is differentiated from trionychid specimens by the regular pattern of the ornamentation. This pattern consists of regularly-spaced and near identical pits lined up in rows across the surface of the shell. In addition to these fragments there are several additional fragments from the Menefee Formation bearing

FIGURE 6. Testudines of the Point Lookout Sandstone a number of incomplete trionychid costals (NMMNH P-28832): left column (dorsal view); right column (ventral view). Scale bar = 2 cm.

FIGURE 5. NMMNH P-42687, second left costal bone of a trionychid turtle from the Dalton Member of the Crevasse Canyon Formation above-dorsal view, below-ventral view. Scale bar = 2 cm.

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FIGURE 7. Adocus sp. NMMNH P-70008 from the Crevasse Canyon Formation including the diagnostic hypoplastran (A-B) and incomplete nuchal (C-D) bones as well as the outwardly curved peripherals (E-F). A, D and E are in ventral view. B, C and F are dorsal view. the same ornamentation present on NMMNH P-25051 and Adocus specimens from the San Juan Basin in the NMMNH collection. Two specimens of Denazinemys and one refered to aff. Denazinemys have been recovered from the Menefee Formation. The smallest of these (NMMNH P-70335) consists of a small ~1 x 4 cm fragment from the proximal end of a costal recognized based on its surface sculpturing and the rib on the ventral surface of the bone. A large number of fragments (NMMNH P-70341) collected from locality L-5768 are tentatively assigned to aff. Denazinemys based on the surface sculpturing seen on 23 of these fragments. There are three fragments from the lateral edge of the anterior lobe of the plastron at least assignable to a baenid. Additionally, mixed in are five pieces that appear to be from a turtle pelvic girdle. These may represent the first girdle material associated with a specimen of Denazinemys. Beyond this the specimen includes approximately 150 indeterminate fragments. Another specimen of Denazinemys nodosa (Fig 8B) is distinguished based on its characteristic surface sculpture (Lucas and Sullivan, 2006). This sculpture is made up of small elongate pustules far less elongate than those seen on Scabremys. Furthermore, the pustules on Boremys are far more densely spaced and generally smaller than those seen on Denazinemys. This is the oldest record of Denazinemys. Additional indeterminate baenid specimens include specimen NMMNH P-70340, which is composed of fragments from locality L-5787, including two large pieces of the lateral edge of the anterior plastral lobe. Further, there are several indeterminate fragments with the specimen. Most of these fragments are weathered smooth, so that sutures and sulci are unrecognizable. The one specimen of the solemydid turtle Naomichelys (Fig. 8C) is a small, ~4 cm diameter piece of turtle shell bone with the characteristic pattern of raised circles seen in this genus (Joyce et al., 2011; Oreska et al., 2013). One sulcus crosses this fragment approximately 1 cm from one of its edges. This represents the only record of Naomichelys from New Mexico.

Trionychids in the Menefee Formation are represented by a number of shell fragments. One nearly complete costal (Fig. 8D), likely between the 3rd and 5th,based on comparison to Meylan (1987), has been collected (NMMNH P-25053). This was identified by Joyce et al. (2011) as a Naomichelys and at the time was imbedded in a block of sandstone. Upon further preparation it was recognized as a trionychid costal. This specimen shows a transition in surface sculpture grading from an ~4 mm pitted pattern near the midline to a more narrow, ~2 mm pitting near the lateral edge. A set of slightly raised ridges run along the length of the shell at ~3 mm spacing. The lateral edge has no pitting and is smooth for ~5 mm from the rounded edge. The ventral surface of this costal shows a pronounced rib ~10 mm wide along the full length of the costal. Additional trionychid specimens, including NMMNH P-70339 and P-70336, from the Menefee Formation are recognized based on their characteristic surface pattern. The largest of the fragments clearly show the plywood structure discussed by Scheyer et al. (2007). At least two additional trionychid specimens from the Menefee Formation are still in preparation. Pelomedusids in the Menefee Formation are represented by only one that is ~70% complete plastron and associated carapace fragments, CHCU 81269, referred to the bothremyid, Elochelys cf. E. perfecta (Fig. 9). This specimen was first published and identified as a pelomedusid by Santucci et al. (2015). This plastron is missing the anterior lobe, and the specimen is heavily weathered. The posterior lobe is broken off just short of the inferred posterior edge. There is no visible surface sculpture on any of the preserved fragments. The posterior lobe of the plastron preserves the medial, abdominal-femoral and femoral-anal sulci. The femoral-anal sulcus meets the medial sulcus at an “S”-shaped juncture in the center of the abdominal lobe. The two sulci are indistinguishable for ~1 cm. The hypo-xiphiplastral suture runs laterally about halfway between the axial notches and the posterior edge of the plastron. The placement of this suture and the pattern of the sulci are similar to that

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FIGURE 8. Turtles of the Menefee Formation: A, Adocus sp. (NMMNH P-25051), left costal? and right incomplete hyoplastron; B, Denazinemys sp. (NMMNH P-42152), incomplete costals; C, Naomichelys sp. (NMMNH P-42161), incomplete costal?; and D, Trionychidae indet. (NMMNH P-25053), near complete costal. Scale bars = 5 cm.

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FIGURE 9. Bothremydid plastron and carapace fragments (CHCU 81269) from the Menefee Formation: A, plastron (ventral view); B, plastron (dorsal view); C, sutures and sulci of the plastron’s posterior lobe with sutures in gray and sulci in black; D, carapace bone fragment in dorsal view (left) and ventral view (right); E, nuchal bone fragment in dorsal view (left) and ventral view (right); F, reconstruction of full nuchal bone based on reflecting preserved portion across the midline; and G, sutures and sulci of the anterior edge of the carapace sutures, in gray and sulci in black. Scale bars = 5 cm.

135seen on bothremydid turtles (Gaffney et al., 2006). The middle portion of the plastron is weathered so that few of the sutures, and none of the sulci, can be definitely placed. What can be seen is the sutures surrounding the narrow mesoplastron show a pattern that is diagnostic of bothremydid turtles (Brinkman and Rodriguez de la Rosa, 2006). In addition to the plastron, parts of two sutured costals and one incomplete nuchal are present. The costals exhibits an interior side of the suture that is deeply embayed. The edges of this fragment are weathered but it retains a trapezoidal shape. This may indicate this bone is originally from one of the narrowing ends of the carapace rather than from the middle of the costal series. The nuchal bone is nearly flat, with the anterior left edge of the carapace preserved. The medial edge of the preserved portion includes a cervical scute with a teardrop shape that comes to a point just beyond the right edge of the fragment. This is unusual in that most known pelomedusids have a sulcus along the midline at the anterior edge and also have an indentation at this point. This nuchal fragment also shows the presence of peripheral scutes approximately 20 mm from the anterior edge to the first costal scute. The anterior edge of this bone is rounded to a nearly circular profile. The sulci on the posterior lobe of the plastron are similar to those seen on Chedighaii and Elochelys in the “S”-shaped meeting of the midline and femoral-anal sulcus, although the anterior margin of the carapace is not emarginated, as in Chedighaii (Gaffney et al., 2006). The cervical scute of this carapace is elliptically shaped with the longer dimension perpendicular to the midline. The forward most part of the carapace of Elochelys perfecta was not preserved. The preserved portions of E. perfecta are largely consistent with what is found on this new specimen. This is the oldest bothremydid turtle in New Mexico and only the second specimen known from New Mexico, the other being Chedhigaii hutchisoni from the upper Campanian Kirtland Formation.

PIERRE SHALE The only turtle fragments known from the Pierre Shale are NMMNH P-16079 and P-16104 (Fig. 10) from locality L-1325. These specimens were originally mis-identified as a mosasaur frontal by Sealey and Lucas (1991). Spielmann et al. (2009) re-classified it as Archelon sp., based on the characteristic grooved surface sculpture of these fragments (Zangerl, 1953; Hirayama, 1997). The internal cortex of the bone is completely weathered away in these fragments. These fragments show the characteristic grooved surface sculpture associated with Archelon on the small portions of the fragments that preserve the external cortex of the shell bone.

RINGBONE FORMATION The Ringbone Formation has yielded only undiagnostic small shell fragments (NMMNH P-8629). This fossil is not diagnostic below the level of the Order Testudines.

FRUITLAND, KIRTLAND AND OJO ALAMO FORMATIONS The extensive collections of fossil turtles from the Fruitland, Kirtland and Ojo Alamo formations were reviewed and revised by Sullivan et al. (2012). They recognized 15 species of turtle in the Fruitland and Kirtland formations. These are the baenid turtles Denazinemys nodosa, Scabremys ornata, Boremys grandis, Thescelus hemispherica, T. rapiens and Neurankylus bauri. The faunas also include two species of adocid turtles, Adocus kirtlandicus and A. bossi and two trionychid turtles of the genus Aspideretoides, A. robustus and A. austerus, as well as many indeterminate fragments of trionychids. The lone putative terrestrial turtle found in these units is Basilemys gaffneyi (Lichtig and Lucas, 2013). Compsemys sp. is known from a number of carapace fragments found in the upper Fruitland Formation and throughout the Kirtland Formation. Finally, the bothremydid turtle Chedighaii hutchisoni is known from a single skull found in these strata (Gaffney et al., 2006; Sullivan et al., 2012). The turtle fauna of the Ojo Alamo Formation is similar to that of the underlying De-na-zin Member of the Kirtland Formation, with the exception of the absence of baenid bone diagnostic below the family level. Furthermore, it differs in the identification of Plastomenus rather than indeterminate plastomenines, as well as Hoplochelys sp. (Jasinski et al., 2011).

MCRAE FORMATION Turtle fossils from the McRae Formation include an indeterminate trionychid fragment (Fig. 11) measuring approximately 10 mm by

FIGURE 10. Two carapace fragments of Archelon sp. NMMNH P-16079 A, dorsal view; B, ventral view. NMMNH P-16104 C, dorsal view; and D, ventral view. Scale bar = 5 cm

20 mm. This identification is based on the surface sculpture of this fragment, which is covered with typical trionychid ornamentation.

CONCLUSIONS Diverse, and arguably understudied, Cretaceous turtle faunas exist outside the San Juan Basin in New Mexico. Virtually all nonmarine Cretaceous formations of New Mexico have turtles, and a similar group of adocid, trionychid and baenid turtles appears to persist throughout the Cretaceous of New Mexico. The turtle assemblage of the Menefee Formation is the second most diverse after the Fruitland and Kirtland formations in New Mexico. Collections from this formation extend the known geographic range of Naomichelys and include the oldest record of Denazinemys. The bothremydid turtle from the Menefee Formation shows a superficial similarity to Pleurodire #1 from Brinkman and Rodriguez De La Rosa (2006), possibly indicating that this species extends into northern New Mexico. The Cretaceous marine and marginal marine formations show a more limited diversity of turtles. Furthermore, in many cases the turtle fauna of these marine units is only represented by one or two shell bones indeterminate beyond the family level. This is likely because the turtle specimens appearing in these marine units derive from marine or shoreline, shark-tooth-dominated assemblages that contain few freshwater fossils. This suggests that most of the turtles found in these assemblages are river dwellers (e.g., trionychids) washed in. This would likely bias collections strongly toward trionychids, which favor larger channels. The turtle assemblages of the coastal floodplain deposits of the Crevasse Canyon, Menefee, Fruitland, Kirtland, and Ojo Alamo formations are generally more diverse. Also of note is the upward trend in diversity in the more recent units from the Crevasse Canyon Formation up to the Kirtland Formation. This also mirrors the collecting effort expended on these units. Further collecting from older units may result in more diversity as well.

ACKNOWLEDGMENTS We thank Amanda Cantrell for her extensive assistance in tracking down the material for this paper, and thank Wendy Bustard for providing access to the bothremydid turtle in the NPS collection in the Hibben Center at the University of New Mexico. We would also like to thank Tom Suazo for his help in preparing several of the turtle

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fossils documented in this paper. Furthermore, Robert Sullivan, helped with a diverse range of information related to this project. Reviews by Adrian Hunt, Steve Jasinski and Robert Sullivan improved the content and clarity of this paper.

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