Frontal projection 

 No filigree 



First incisor 



Low-crowned, rooted teetti 



Long incisive foromino 



Incisors 



Frontal projection 



Bony swelling for cheek-feeft^ 



Prismatic teeth witti folded enamel pattern 

 Incisive foramina 

 Incisors 



Fine details of the skull show that the 



fifty-five-million-year-old Naran Bulak 



animal was starting to become more 



like a modem lagomorph. A side view 



(h) of the skull reveals two pairs of 



incisors (blue), and a frontal bone 



(purple) that juts foi-ward; but no 



network of openings on the snout. (The 



diagonal stripes indicate rocky 



matrix.) A view of the upper jaw and 



palate (B) shows this animal's 



rodentlike, low-crowned teeth and 



relatively long palate; but unlike a 



rodent's, its incisive foramina 



openings are long. 



and by later expeditions (including our 

 own in tiie 1990s). Now Zalambdalestes. 

 too, seems to me to be a distant relative of 

 lagomorphs — closer to them than to many 

 other kinds of mammals because it seems 

 to share at least a few derived features 

 with them, the rest of its features being ei- 

 ther primitive characteristics that were not 

 later modified or peculiarities unique to it. 

 This conclusion may be proved wrong by 

 study of further evidence, but perhaps the 

 relationships of lagomorphs to other mam- 

 mals have been available to us all along, 

 right in museum collections, unappreci- 

 ated. That is why museums need to keep 

 and augment large collections for future 

 researchers. Someday, someone may see a 

 specimen in our collections that has fea- 

 tures currently unknown to paleontolo- 

 gists, or someone may be able, through 

 new insight, to reinterpret prevailing ideas 

 in a new and interesting way. 



A Palaeolagus species from thirty- 

 five-million-year-old North 

 American rocks reveals a much 

 more rabbitlike creature. Visible 

 from the side (C) is the frontal bone 

 projection (purple), as well as a 

 rabbitlike lacy filigree on the snout 



and a swelling that housed the 



cheek-teeth. The palatal view (D) 



shows that the incisive foramina 



are still long, but the palate is 



short, the first incisors are grooved, 



the second incisors small (blue), 



and the cheek-teeth are prismatic, 



with enamel patterning, more 



appropriate for a lagomorph 's diet 



than a primitive manmial's. 



Illustrations by Ed Heck 



58 Natural History 4/94 



