zalambdalestes - American Museum of Natural History

More documents

Recommendations

Info

118 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 Other similarities taken from Archibald et al. (2001) include the bases of paracone and metacone separate, a crista interfenestralis connected to the caudal tympanic process of the petrosal by a curved ridge, a ‘‘tympanic process’’ of Kielan-Jaworowska (1981) present (the lateral half of which is on the petrosal), and the absence of a transpromontorial sulcus. According to Archibald and Averianov (2003), Kulbeckia resembles Zalambdalestes in having a translacrimal canal (although it is placed more ventrally in Kulbeckia), a lacrimal tubercle, a weak postorbital process on the frontal, the infraorbital foramen at the level of the penultimate premolar, the second upper incisor more laterally compressed than the first, a probable two-rooted upper canine, and the mental foramina below p1 and p3 (fig. 51A, C). The condition of the first three features is unknown in Barunlestes, whereas the last two differ in that taxon (see above). Finally, Kulbeckia resembles some specimens of Zalambdalestes in having a small third upper incisor within the maxilla. According to Archibald and Averianov (2003), Kulbeckia differs from Zalambdalestes and Barunlestes in the ‘‘probable retention of four lower incisors, bifurcated or tworooted lower canine, relatively smaller or absent diastemata between anterior teeth, more lingually placed cristid obliqua, less reduced M3 and m3’’, lack of a metaconal swelling on P4, lingually placed conules on M1 and M2 (with distinct, low internal cristae), upper molar protocones usually with small vertical crenulation or small cuspule on the anteroand posterolingual margins of well-developed cingula, and trigonids not as anteroposteriorly shortened. Additionally, Kulbeckia differs from Zalambdalestes in having what appears to be a foramen for the frontal diploic vein (Thewissen, 1989) in the frontal bone ventral to the postorbital process, vertically implanted upper incisors, I1 and I2 subequal, I2 in the premaxillary-maxillary suture (fig. 51A, C), and a lower stapedial ratio, 1.52–2.54 with an average of 1.88 for Kulbeckia (but see comments above) versus 2.3 for Zalambdalestes. WITH LEPTICTIDS AND INSECTIVORANS: As noted earlier, Gregory and Simpson (1926a) speculated based largely on dental evidence that zalambdalestids were stem ‘‘zalambdadonts’’. After studying the better preserved dentition of AMNH 21709 (Simpson, 1928a), Simpson (1928b) revisited the wider relationships of zalambdalestids and altered his earlier conclusion. He disassociated Zalambdalestes from ‘‘zalambdadonts’’ and allied them with leptictids, noting the remarkable similarity in molar structure. Close relationships between zalambdalestids and early Tertiary leptictids have been supported subsequently by McDowell (1958), Van Valen (1967), Kielan-Jaworowska (1969a), and Clemens (1973). More recent comparisons have uncovered few derived resemblances in the dentition or skull of zalambdalestids and leptictids (Novacek, 1986a; Clemens and Lillegraven, 1986). Among the few cranial resemblances of zalambdalestids and leptictids that are unusual in their incidence among eutherians are a large, common recess for the foramina transmitting the major palatine and caudal nasal nerves and vessels (known in Zalambdalestes) and a suprameatal foramen (known in Zalambdalestes and Barunlestes) (fig. 53). According to Novacek (1986a), the sphenopalatine recess also occurs in lipotyphlans, carnivorans, and aardvarks, and the suprameatal foramen is also in didelphids as well as some xenarthans and euprimates. The spenopalatine recess also occurs in asioryctitheres (Kielan-Jaworowska, 1981), and the suprameatal foramen may be primitive, because it is also present in basal metatherians (Rougier et al., 1998) and in asioryctitheres (see below). Other cranial similarities (fig. 53) include a long anterior process of the alisphenoid that contacts the palatine (known in Zalambdalestes), well-develped ecto- and entopterygoid crests (known in Zalambdalestes and Barunlestes), and a small palatine contribution to the orbital wall (known in Zalambdalestes and Barunlestes). A long anterior process of the alisphenoid in contact with the palatine also occurs in some extant placentals (fig. 54; Muller, 1934; McDowell, 1958) and marsupials (Wible, 2003), but it is lacking in Vincelestes (Rougier, 1993; Hopson and Rougier, 1993), the basal metatherian Pucadelphys (Marshall and Muizon, 1995), asioryctitheres (Kielan-Jaworowska, 1981), Daulestes (McKenna et al., 2000),
2004 WIBLE ET AL.: ZALAMBDALESTES 119 Fig. 53. The skull and lower jaw of the leptictid Leptictis dakotensis in right lateral view, redrawn from Novacek (1986a: figs. 1, 10). Parallel lines indicate the cut surfaces of the zygoma. Abbreviations: an, (mandibular) angle; ap, anterior process of alisphenoid; as, alisphenoid; asc, alisphenoid canal; con, (mandibular) condyle; ecpc, ectopterygoid crest; en, entotympanic; enpc, entopterygoid crest; fdv, foramina for frontal diploic vein; fr, frontal; lact, lacrimal tubercle; ma, mandible; mx, maxilla; os, orbitosphenoid; pa, parietal; pal, palatine; pmx, premaxilla; smf, suprameatal foramen; sq, squamosal; ssf, subsquamosal foramen. and the Eocene palaeoryctid Eoryctes (Thewissen and Gingerich, 1989). Well-developed ecto- and entopterygoid crests also occur in asioryctitheres (fig. 56B; Kielan-Jaworowska, 1981) and some extant placentals (Novacek, 1986a), but they are lacking in Vincelestes (Rougier, 1993), Daulestes (Mc- Kenna et al., 2000), and Eoryctes (Thewissen and Gingerich, 1989). Regarding the palatine in the orbit, a small contribution also occurs in some extant placentals (fig. 57; Muller, 1934; Novacek, 1980, 1985), but it is more extensive in Vincelestes (Rougier, 1993), metatherians (Wible, 2003), asioryctitheres (Kielan-Jaworowska, 1981), Daulestes (Mc- Kenna et al., 2000), and Eoryctes (Thewissen and Gingerich, 1989). Leptictids resemble Barunlestes, and not Zalambdalestes, in that the palatine contacts the lacrimal (fig. 53). Leptictids differ from zalambdalestids in numerous features including the presence of a well-developed entotympanic bulla, absence of a foramen rotundum, broad dorsal contact between the maxilla and frontal, and small facial exposure of the lacrimal (fig. 53). Two recent phylogenetic analyses have linked leptictids and Zalambdalestes. In Rougier et al.’s (1998) analysis of the relationships of Deltatheridiidae, which included seven eutherian taxa altogether, Zalambdalestes was identified as the sister taxon of Leptictis in a clade with ‘‘zhelestids’’ (fig.
Page 1 and 2:
NEW DATA ON THE SKULL AND DENTITION
Page 3 and 4:
2004 WIBLE ET AL.: ZALAMBDALESTES 3
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68: 2004 WIBLE ET AL.: ZALAMBDALESTES 6
Page 117: 2004 WIBLE ET AL.: ZALAMBDALESTES 1
show all

zalambdalestes - American Museum of Natural History

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?