Dirqadim, Gaffney & Tong & Meylan, 2006

GAFFNEY, EUGENE S, TONG, HAIYAN & MEYLAN, PETER A, 2006, EVOLUTION OF THE SIDE-NECKED TURTLES: THE FAMILIES BOTHREMYDIDAE, EURAXEMYDIDAE, AND ARARIPEMYDIDAE, Bulletin of the American Museum of Natural History 300 (300), pp. 1-698 : 41-44

Dirqadim , new genus

TYPE AND ONLY INCLUDED SPECIES: Dirqadim schaefferi , n. sp.

DISTRIBUTION: Cenomanian, Late Cretaceous of Morocco.

ETYMOLOGY: Dir, Arabic for armor; qadim, Arabic for ancient. We are very grateful to the help of Mark Caponigro for this etymology.

DIAGNOSIS: Euraxemydid Pelomedusoides differentiated from Euraxemys by parietal-squamosal contact present; temporal emargination less extensive; quadratojugal not exposed on temporal margin; skull shorter and wider; labial ridge broader; accessory ridge on premaxilla present; median concavity on premaxilla present; labial ridge curved, convex ventrally in lateral view; triturating surface parallel sided; accessory ridge on maxilla strongly developed; antrum postoticum smaller; prootic-opisthotic contact broader; median pterygoid contact shorter; ventral opening into canalis cavernosus just lateral to foramen posterius canalis carotici interni present; foramen posterius canalis carotici interni with prootic in margin as well as pterygoid and basisphenoid; foramen nervi vidiani not exposed in ventral view.

DISCUSSION: See table 3 for generic comparison.

Dirqadim schaefferi , new species

TYPE SPECIMEN: MDEt 41, a nearly complete skull (figs. 44–53).

TYPE LOCALITY: Eastern Morocco, Kem Kem region (figs. 14, 15). The fossil turtles ( Hamadachelys , Galianemys , and Dirqadim ) were collected by the local people and obtained from private collectors and dealers; their exact geological origin is therefore uncertain. However, all specimens clearly come from the Cretaceous red beds in the region called Hamada du Guir, or Kem Kem, in the southeast part of Morocco. The area is also called the Tafilalt by the local people. These terms are sometimes confusing. In fact, according to Lavocat (1954), the Hamada du Guir is a vast desert plateau east of the town of Taouz, extending from north to south, and the Kem Kem is southwest of Taouz, which is quite different from the Hamada in its structure and physiognomy ( Lavocat, 1954). The vertebrate-bearing red beds, termed as ‘‘Kem Kem beds’’ by Sereno et al. (1996), outcrop along the border of the Hamada du Guir to the Kem Kem, from north of the town of Erfoud to the south for some 250 km. Along this distance, local people dig underground galleries to find vertebrate fossils, for the local and international fossil market.

The most important work on the geology of this region was made by Lavocat in the late 1940s and early 1950s ( Lavocat, 1954). The continental red beds from which the vertebrate remains are derived are represent- ed by a formation of ca. 200-m maximum thickness. They include two units: the lower unit is composed of red detritic crossstratified sandstones, of channel-fill deposits, and the upper unit is composed of red to tan sandstones intercalated with mudstones, indicating a change in sedimentation rates. Both units contain vertebrate remains. These red beds lie unconformably on the Paleozoic basement and are covered by a limestone platform formed by the Cenomanian–Turonian transgression. The vertebrate-bearing beds have therefore been termed ‘‘Infra- Cenomanian’’ by Lavocat (1954) and were long considered as Albian in age ( Forey and Grande, 1998; Taquet, 1976). The base of the overlying Cenomanian–Turonian limestones in the area of Erfoud Errachidia and the Taouz region is dated by the occurrence of the ammonite Neolobites vibrayeanus ( Basse and Choubert, 1959; Ferrandini et al., 1985). The vibrayeanus Zone , which is known in many parts of the Tethyan regions, corresponds to the base of the late Cenomanian ( Courville et al., 1991). The age of the vertebrate-bearing red beds is therefore older than late Cenomanian, but their oldest age is not well constrained stratigraphically.

Comparisons have been made between the vertebrate assemblage of Kem Kem beds and those from nonmarine deposits of other parts of Sahara and surrounding areas. As recognized by Lavocat (1954), the Kem Kem vertebrate fauna closely resembles that of Baharia, discovered by Stromer (1936) in Egypt. Several theropod dinosaurs, Spinosaurus and Carcharodontosaurus , and crocodilian Libycosuchus occur in both localities ( Buffetaut, 1989a, 1989b, 1989c; Sereno et al., 1996; Tong and Buffetaut, 1996; Wellnhofer and Buffetaut, 1999). The Baharia assemblage was considered as Cenomanian in age by Stromer (1936). More recent works on fossil fishes from Baharia confirm Stromer’s opinion ( Slaughter and Thurmond, 1974; Schaal, 1984). According to Dominik (1985), the main vertebrate-bearing bed of the Baharia Formation includes marine intercalations, and the occurrence of the ammonite Neolobites indicates a late Cenomanian age for the Baharia deposits.

According to Sereno et al. (1996), nine elasmobranch species from the Kem Kem beds support a Cenomanian age for the deposits; seven of them occur also in the Cenomanian Baharia Formation, including four species limited to these formations ( Distobatus nutiae , ‘‘ Lissodus ’’ bartheli, Markgrafia libyca , and Peyeria libyca ), and one species ( Serratolamna amonensis ) occurs with a broad distribution and is restricted to the Cenomanian. The later species ‘‘ Serratolamna ’’ amonensis , probably called Carcharias amonensis , is indeed restricted to the Cenomanian according to Cappetta and Case (1999). Thus, even though the shark and ammonite evidence does not precisely agree, the Cenomanian age for the Kem Kem beds is now widely accepted.

The Cenomanian Kem Kem beds have yielded abundant and very diverse vertebrate assemblages, which consist mostly of nonmarine species: fishes ( Wenz, 1981; Martin 1984a, 1984b; Tong and Buffetaut, 1996; Forey, 1997; Forey and Grande, 1998; Dutheil, 1999a, 1999b; Taverne and Maisey, 1999; Cavin and Brito, 2001; Cavin et al., 2001), lizards, crocodiles ( Buffetaut, 1994; Larsson and Sidor, 1999), turtles ( Tong and Buffetaut, 1996; Gaffney, Tong, and Meylan, 2002), pterosaurs ( Mader and Kellner, 1999; Wellnhofer and Buffetaut, 1999), and dinosaurs ( Lavocat, 1951; Buffetaut, 1989a, 1989b; Russell, 1996; Sereno et al., 1996). The depositional environment is supposed to be deltaic or fluvial ( Sereno et al., 1996; Cavin et al., 2001), and some fossil fishes found in one limited site indicate a still-water environment, like a lake or pool ( Dutheil, 1999a).

HORIZON: Cenomanian Kem Kem beds.

DEPOSITIONAL ENVIRONMENT: Deltaic or fluvial ( Sereno et al., 1996; Cavin et al., 2001), found with dinosaurs and other freshwater/terrestrial fauna.

DIAGNOSIS: Same as genus.

ETYMOLOGY: In honor of Dr. Bobb Schaeffer (1913–2004), former Curator of Fossil Fishes at the Department of Vertebrate Paleontology, American Museum of Natural History, and close friend and mentor of the senior author.

REFERRED MATERIAL: AMNH 30038, skull lacking anterior half, Kem Kem, Morocco.

PREVIOUS WORK: None.

SUPERFAMILY PODOCNEMIDOIDEA COPE, 1868

TYPE GENUS: Podocnemis Wagler, 1830 .

INCLUDED TAXA: Family Bothremydidae and epifamily Podocnemidinura (consisting of the family Podocnemididae , genera Hamadachelys Tong and Buffetaut, 1996 ; Brasilemys Lapparent de Broin, 2000b ; and Portezueloemys Fuente, 2003 ).

DIAGNOSIS: Magnafamily Podocnemidera uniquely in possession of a quadrate-basioccipital contact; prootic completely or almost completely covered ventrally by quadrate, basisphenoid, and pterygoid; dentary symphysis fused, not sutured, as in Euraxemydidae , Teneremys , and Araripemys ; pectoral scales on entoplastron (except in a few Bothremydidae ).

DISCUSSION: This taxon consists of the epifamily Podocnemidinura (the Podocnemididae plus its near relatives, Hamadachelys , Brasilemys , and, presumably, Portezueloemys ) and the Bothremydidae . This superfamily name is in the sense of its original author, Broin (1988), and later, Lapparent de Broin (2000b, 2001). Meylan (1996) used ‘‘Podocnemoidae’’ for this group, which we have avoided.

EPIFAMILY PODOCNEMIDINURA COPE, 1868

TYPE GENUS: Podocnemis Wagler, 1830 .

INCLUDED TAXA: Family Podocnemididae , genera Hamadachelys Tong and Buffetaut, 1996 ; Brasilemys Lapparent de Broin, 2000b ; and Portezueloemys Fuente, 2003 .

DIAGNOSIS: A member of the superfamily Podocnemidoidea uniquely possessing a cavum pterygoidei formed by basisphenoid, pterygoid, prootic, and quadrate, underlain by pterygoid and basisphenoid (in contrast to fossa pterygoidea of some Bothremydidae ); processus retroarticularis of articular oriented posteroventrally; basioccipital-opisthotic contact present (also in Pelomedusidae and some Chelidae , not known in Brasilemys ).

DISCUSSION: Our analysis agrees with Lapparent de Broin (2000b) and Fuente (2003) in that the close relatives of the Podocnemididae have this relationship: ( Brasilemys ( Hamadachelys ( Podocnemididae ))). We also follow their restricted use of the family Podocnemididae and do not place Brasilemys or Hamadachelys (or Portezueloemys ) within it. Table 4 compares the skull in the three groups; the shell is not yet known for Hamadachelys .

We do not use the Lapparent de Broin (2000b) name ‘‘Podocnemidoidae.’’ Instead, we create a new name, the epifamily Podocnemidinura, for the identical content and concept, even though the Lapparent de Broin name is older. The ‘‘Podocnemidoidae’’ is so close in spelling to Podocnemidoidea , which

TABLE 4 Comparison of Podocnemidinura has a different content, that we think its continued use too confusing. This is permissible under the current rules for higher categories.

Although we agree with Fuente (2003) that Portezueloemys is a closer relative of the Podocnemididae than either Brasilemys or Hamadachelys , we have not included it in our analysis due to the high missing values in the skull characters and because we have been unable to examine the specimen.

Brasilemys Lapparent de Broin, 2000b

TYPE AND ONLY INCLUDED SPECIES: Brasilemys josai Lapparent de Broin, 2000b .

DISTRIBUTION: Albian, Brazil.

ETYMOLOGY: For Brazil, country of origin ( Lapparent de Broin, 2000b).

REVISED DIAGNOSIS: Member of the epifamily Podocnemidinura with the cavum pterygoidei partially developed, as in Hamadachelys , but in contrast to complete as in Podocnemididae ; quadratojugal-parietal contact absent, in contrast to Hamadachelys and Podocnemididae ; incisura columellae auris not enclosing stapes and eustachian tube with bone, in contrast to Hamadachelys and Podocnemididae ; dentary widely exposed on lateral surface of lower jaw, as in Hamadachelys , but in contrast to Podocnemididae ; fossa precolumellaris shallow, in contrast to Hamadachelys and Podocnemididae ; foramen jugulare posterius partially closed, in contrast to open, as in Hamadachelys and Podocnemididae ; exoccipital-quadrate contact present, in contrast to Hamadachelys and Podocnemididae . See also Lapparent de Broin, 2000b.