Cimolestidae

Wible, JR, Rougier, GW, Novacek, MJ & Asher, RJ, 2009, The Eutherian Mammal Maelestes Gobiensis From The Late Cretaceous Of Mongolia And The Phylogeny Of Cretaceous Eutheria, Bulletin of the American Museum of Natural History 2009 (327), pp. 1-123 : 60-62

Cimolestidae

In the consensus tree, Maelestes is in a clade with two North American genera, Cimolestes and Batodon , as sister to the latter (fig. 29: M 1, 30). Wible et al. (2007) referred Maelestes to Cimolestidae , which according to Kielan-Jaworowska et al. (2004) included Cimolestes and Batodon along with Telacodon Marsh, 1892 , and Procerberus Sloan and Van Valen, 1965 , from the North American Late Cretaceous and a number of unnamed Tertiary genera. The relationships of the taxa in Cimolestidae sensu Kielan-Jaworowska et al. (2004) and Cimolestidae sensu McKenna and Bell (1997) , which included Cimolestes , Procerberus , and 11 early Tertiary genera from North America, Europe, Africa, and Asia, are in need of revision, but beyond the scope of this report. Strauss (2007), in fact, recognizes Cimolestidae as paraphyletic. Rose (2006a), Kielan-Jaworowska et al. (2004), and McKenna and Bell (1997) included Cimolestidae within Ferae , which also included creodonts and carnivorans. This relationship is not supported by Wible et al. (2007), the only phylogenetic analysis to test this hypothesis to date. Here we compare Maelestes , Batodon , and Cimolestes .

Batodon tenuis Marsh, 1892 , is a rare, poorly known form from the Lance ( Simpson, 1929; Clemens, 1973; Storer, 1991), Edmonton ( Lillegraven, 1969), and Hell Creek Formations ( Archibald, 1982; Hunter and Archibald, 2002; Wood and Clemens, 2001). There are only a few fragmentary specimens and isolated teeth. The lower dentition (fig. 32) is known from the canine, four premolars, and three molars (the canine is broken and only the p1 alveolus is known); the upper dentition is known from the last premolar (isolated) and three molars. It is among the smallest Cretaceous eutherians, its weight estimated at just over five grams ( Wood and Clemens, 2001), which probably accounts for its poor record. B. tenuis has been identified as a geolabidid soricomorph lipotyphlan ( Krishtalka and West, 1979; McKenna and Bell, 1997; Bloch et al., 1998), but we support close ties with Cimolestes as did Lillegraven (1969) and Kielan-Jaworowska et al. (1979, 2004).

Kielan-Jaworowska et al. (2004) included five Cretaceous (Lance and Hell Creek Formations) and one Paleocene (Puercan) North American species in Cimolestes . A second Paleocene species, Cimolestes cuspulus Gheerbrant, 1992 , from Morocco was named based on several isolated, broken teeth ( Gheerbrant, 1992). According to several authors (e.g., Archibald, 1982; Fox, 1989; Strauss, 2007), Cimolestes is a grade taxon in need of revision. Nevertheless, Wible et al. (2007) used all six species in scoring Cimolestes (see appendix 1), although they mistakenly omitted Cimolestes cerberoides Lillegraven, 1969 , from their taxon list. Cimolestes also is said to be present in the Paleocene of Bolivia ( Marshall and Muizon, 1988). The entire lower dentition (two incisors, canine, four premolars, and three molars) is known only for the type of Cimolestes propalaeoryctes Lillegraven, 1969 , KU 3756 (fig. 32), although it could not be determined if a third incisor was present ( Lillegraven, 1969); Cimolestes incisus Marsh, 1889 , UCMP 46874 (fig. 32) preserves alveoli for three incisors ( Clemens, 1973). The most complete upper dentition is known for the type of Cimolestes simpsoni ( Reynolds, 1936) , the Puercan species, UCMP 36658, an anterior skull fragment with P2, P4, P5, M1–M3, and alveoli for the canine and P1 ( Reynolds, 1936; Van Valen, 1966; Clemens, 1973).

Six unequivocal synapomorphies unite Maelestes , Batodon , and Cimolestes (appendix 4: node M 1), but the distribution of the first three is not well known for either Batodon or Cimolestes . The anteriormost and posterior lower incisors are procumbent (characters 17 and 21), but the condition is unknown in Batodon and the teeth are preserved only in C. propalaeoryctes KU 3756 ( Lillegraven, 1969), although the parts of the three preserved incisor alveoli in C. incisus UCMP 46874 suggest the presence of procumbent teeth (fig. 32). The P1 and p1 are single rooted (characters 33 and 48), but the P1 or its alveolus is unknown in Batodon and only on the right side of C. simpsoni UCMP 36658; the P1 alveolus is absent on the specimen’s right side ( Reynolds, 1936; Van Valen, 1966). The p1 or its alveolus is known in Batodon ( Simpson, 1929; Lillegraven, 1969; Clemens, 1973) and C. incisus , C. cerberoides , and C. propalaeoryctes ( Lillegraven, 1969; Clemens, 1973) (fig. 32). The p5 talonid is narrower than the anterior portion of the crown (character 57), which is known in Batodon ( Clemens, 1973; Archibald et al., 2001) and Cimolestes magnus Clemens and Russell, 1965 , C. incisus , C. cerberoides , and C. propalaeoryctes ( Lillegraven, 1969; Clemens, 1973). Lastly, there is the lingually placed M2 protocone (character 95), which is known for Batodon (Archibald et al., 2001; Wood and Clemens, 2001) and the studied species of Cimolestes ( Lillegraven, 1969; Clemens, 1973; Archibald et al., 2001) (fig. 33).

Five unequivocal synapomorphies unite Maelestes and Batodon (appendix 4: node M 2). The first four are molar features that highlight the greater similarity of the molars of Maelestes and Batodon compared to those of Cimolestes (figs. 33, 34). On the upper molars (M2), the stylar shelf is less then 25% of the total tooth width (character 65) and the preparacingulum is interrupted between the stylar margin and the paraconule (character 75); the stylar shelf is wider and the preparacingulum is not interrupted in Cimolestes . On the lower molars (m2), the protocristid is transverse (character 113) and the hypoconulid is lingually placed with slight approximation to the entoconid (character 120); the protocristid is oblique and the hypoconulid is in a posteromedial position in Cimolestes . Lastly, the anteriormost mental foramen is below p2 (character 129); it is below p 1 in C. incisus UCMP 46874, C. cerberoides KU 3054; and C. propalaeoryctes KU 3756 (fig. 32).

Maelestes differs from Batodon and Cimolestes in the presence of P3 and p3, presence of pre- and postcingulum on P5, p5 that is shorter than p4, presence of weak upper molar conules, lower molars with more compressed trigonids, protoconid subequal to metaconid, and postcristid nearly transverse and taller than hypoconulid. Batodon differs from Maelestes in having a metaconid swelling and anterolingual cingulid on p5, and shallow ectoflexus and metacone only slightly smaller than paracone on M2.