zalambdalestes - American Museum of Natural History

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46 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 281 Fig. 20. Stereophotograph of the skull of Zalambdalestes lechei PSS-MAE 135 in dorsal view, with accompanying line drawing. Gray pattern represents matrix; parallel lines are damaged surfaces. Abbreviations: fr, frontal; lac, lacrimal; lacf, lacrimal foramen; ma, mandible; mx, maxilla; na, nasal; nc, nuchal crest; pa, parietal; paf, parietal facet on frontal; pop, postorbital process; sc, sagittal crest; sq, squamosal; tl, temporal line; tlc, translacrimal canal. palatine suture, which is filled with matrix, and expands laterally into the strong postpalatine torus (figs. 35, 43). Kielan-Jaworowska (1984a) reported the postpalatine torus as very faint based on ZPAL MgM-I/14 and 16, the condition scored for Zalambdalestes by Rougier et al. (1998) in their phylogenetic analysis. In PSS-MAE 130, immediately lateral to the postpalatine torus and medial to M3, is a large, oval opening, the minor palatine foramen, which communicates directly with the anteroventral portion of the orbit (fig. 35). The bones forming the foramen are clearly seen on the left side of PSS-MAE 130. Anteriorly, medially, and posteromedially, it is the palatine, laterally the maxilla, and posteriorly the pterygoid. This contrasts with the reconstruction of Kielan-Jaworowska (fig. 4D; 1984a: fig. 1), which places the maxilla on the posterior border of the foramen, and of Van Valen (fig. 4C; 1964: fig. 2), which shows only a posterior palatine notch, the condition preserved in AMNH 21708 (fig. 32) but probably the result of damage. The minor palatine foramen in life was slightly smaller than as shown on the left side of PSS-MAE 130, in which the part of the maxilla and palatine forming the anterior border are damaged (figs. 8A, 35). Anteromedial to the minor palatine foramen in PSS-MAE 130, in the anterolateral surface of the base of the postpalatine torus is a small, anteriorly directed, circular foramen of uncertain function. Present bilaterally, this aperture seems too far posteriorly positioned to be an accessory pal-
2004 WIBLE ET AL.: ZALAMBDALESTES 47 Fig. 20. Continued. atine foramen. Wible (2003) reported similar foramina piercing the postpalatine torus in the didelphid Monodelphis. ORBITOTEMPORAL REGION: Virtually nothing about the orbit was known from the CAE specimens of Zalambdalestes (see fig. 19), according to Gregory and Simpson (1926a). The reconstruction by Van Valen (fig. 4A; 1964: fig. 2) does include sutures in the orbit, but we cannot identify or confirm these on the CAE or MAE specimens. The Warsaw material has provided information only about the principal orbital foramina (Kielan-Jaworowska, 1984a). Four MAE specimens, PSS- MAE 108 (figs. 23–25), 129 (fig. 31), 130 (figs. 26–29), and 135 (fig. 30), preserve aspects of the orbital region, and between them, most features can be recognized, although not all sutures can be reconstructed with total certainty. The anterior orbit is best preserved in PSS-MAE 108 and 135. The posterior orbit is best represented in PSS- MAE 130, although the identification of some sutures is confounded by numerous cracks. Finally, aspects of the temporal fossa are preserved in PSS-MAE 108, 130, and 135, as well as in AMNH 21708. The lacrimal is a large element at the anterodorsal apex of the orbit. In addition to its facial process described above, the lacrimal forms a large wedge in the anterior wall of the orbit, based on the left side of PSS-MAE 108 (fig. 24), 130, and 135. Its contacts within the orbit are with the maxilla inferiorly and the frontal medially. The suture with the maxilla, preserved in PSS-MAE 108 (fig. 24) and 135, is essentially straight, except at its lateral terminus where is runs obliquely dorsally. At the medial edge of the maxillo-lacrimal suture is the maxillary foramen, the posterior entrance into the infraorbital canal, which is a transversely oriented, elongate, oval aperture (fig. 24). No specimen preserves the entire suture with the frontal, but enough is preserved between PSS-MAE 108 (fig. 24), 130, and 135 to say that the suture was largely vertical. Two lacrimal foramina are preserved in a shallow depression just inside the orbital rim above the suture between the lacrimal and maxilla on the left side in PSS-MAE 108 (fig. 24) and 135. The orbital rim lateral to the more superior lacrimal foramen is thickened and bears a weak lacrimal tubercle (fig. 23; also in AMNH 21708, figs. 4A, 19; see Van Valen, 1964: fig. 2). Gregory and Simpson (1926a) reported only a single lacrimal foramen (but see below). Preserved on both sides in PSS-MAE 108 (fig. 24) and 135, dorsomedial to the lacrimal foramina is another aperture within the lacrimal somewhat more recessed from the orbital rim; the corresponding part of the lacrimal is missing in PSS-MAE 130. This oval foramen runs through a short canal that opens on the facial process of the lacrimal. The facial opening of this canal is just outside the orbital rim in PSS-MAE 108 (figs. 18, 23), whereas it is separated by a wider bridge of bone from the orbital rim in PSS-MAE 135 (figs. 20, 30). This canal was discovered upon restudy of the left side of AMNH 21708 (figs. 17, 22), with a facial aperture resembling that in PSS- MAE 135. We think the orbital aperture of this canal was mistakenly identified as the lacrimal foramen by Gregory and Simpson (1926a); the part of the lacrimal bone showing two lacrimal foramina in PSS-MAE 108 and 135 is not preserved in AMNH 21708.
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zalambdalestes - American Museum of Natural History

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