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A Comparison of Pipilo Ocai and the Fossil Pipilo Angelensis

William R. Dawson
Publication Information
2 (March-April)
From Field and Study

A Comparison of Pipilo ocai and the Fossil Pipilo angelensis.-A comparison of Pipilo angelensis of the Rancho La Brea Pleistocene and Pipilo ocai of Mexico was not made in the description of the fossil (Dawson, Condor, 50, 1948:57-63) due to the lack of comparative material of the latter. Through the kindness of Alden H. Miller, a specimen of ocai, recently acquired by the Museum of Vertebrate Zoology, has been made available for my study. The comparison is of the premaxillary and associated parts which form the upper mandible, the element which serves as the type of Pipico angelensis.

Pipilo ocui lacks the short longitudmal ridge found in the fossil just medial to the junction of the superior and inferior nasal processes on the superior process. The profile of the intemarial bridge is more elevated than that of Pipilo angelensis and drops more abruptly to join the posterior part of the premaxillary. In addition to the marked differences in shape, Pipilo ouri, judging from the one specimen examined, seems to have a longer premaxillary and higher, though relatively shorter, nares than the fossil (see table). All measurements suggest that the Pleistocene towhee was a smaller bird than the Recent Pifilo ocai.

Measurements in mm.                                       Type                     Cotype     

(a) Width across maxillaries                                 7.6                        7.6                 8.4

(b) Height at front of nares                                   3.1                        2.9                 3.8

(c) Length from anterior end of nares to tip           8.72                       8.7                 9.4 

of mandible              

(d) Length of nostril                                            5.4                         5.3                 5.3

(e) Height of nostril                                             3.2                        3.1                  3.8

Ratios (in per cent)

a to c                                                                87.3                     87.3                89.4

b to a                                                                40.8                      38.1               45.2 

d to c                                                                62.1                      60.9               56.4

e to d                                                                59.3                      58.3               71.7

WILLIAM R. DAWSON, University of California at Los Angeles,  August 8, 1949.

Total votes: 0

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