A late Cretaceous callorhynchid (chondrichthyes, holocephali) from Seymour Island, Antarctica

TY - JOUR

T1 - A late Cretaceous callorhynchid (chondrichthyes, holocephali) from Seymour Island, Antarctica

AU - Stahl, Barbara J.

AU - Chatterjee, Sankar

N1 - Funding Information: the Lopez de Bertodano Formation and opportunities for scavenging in shallow seawaters are common, it is possible that the Antarctic chi-maeroids had radiated by adapting different feeding habits early in their history. Although the holocephalians were much reduced in variety by the Mesozoic and had diminished to the chimaeroids alone by the end of the era, the latter fishes as a group survived the biotic stresses of late Cretaceous time to persist into the Cenozoic. The discovery of a mandibular tooth plate of Maastrichtian age referable to Ischyodus dolloi, known hitherto only from Paleocene and Eocene specimens, extends the chronological range of this species by 12 million years and puts into the fossil record the first species of chimaeroid to cross the K-T boundary. It was widespread in the early part of the Cenozoic, having been reported from the Paleocene of Belgium and France (Leriche, 1902) and North Dakota, USA (Cvancara and Hoganson, 1993), from the Paleocene/Eocene of Russia (Popov, 1996), and the Eocene of Eng- land (Gurr, 1963 [for 1962]; Ward, 1973), and now from the Eocene of Antarctica. The callorhynchids disappeared from the northern hemi-sphere after the Eocene, but L dolloi may have persisted in southern seas throughout the Tertiary period: N. Kemp (in Vickers-Rich et al., 1991:518) referred a tooth plate from the upper Miocene-lower Pliocene of Australia to this species provisionally, and Ward and Grande (1991) suspect that a palatine, also from deposits of Miocene-Pliocene age in Australia, described as Chimaera anomala by Woodward and White (1930) may be, in fact, a peculiar variant of Ischyodus. The mandibular tooth plate from the Lopez de Bertodano Formation, the oldest example of L dolloi known, may represent an early member of the species. L dolloi is not among the 21 species recorded from European Jurassic deposits formed when Ischyodus first appeared and radiated. Nor is L dolloi represented among the nine new species added from Cretaceous strata in Europe and Russia. Popov (1996) constructed a morphologic series based on mandibular tooth plates in which he posited a succession of species of Ischyodus culminating in the Paleo- cene-Eocene L. dolloi. On the evidence now available, one might speculate that L dolloi could have originated in the high latitudes in the sea around Antarctica and migrated into the waters of the north to replace the populations of Ischyodus already there. The early record of L dolloi in Antarctica and the subsequent dis-persal northward of this species fit a pattern of high latitude hetero-chroneity (differential appearance of taxa between high and mid-to low latitudes), as seen among a wide spectrum of faunas and floras. Zins-meister and Feldmann (1984) identified in the Early Tertiary La Meseta Formation of Seymour Island eleven genera of invertebrates that pre- dated their mid-latitude descendants by as much as 40 million years. They concluded that the high latitude of the Southern Hemisphere acted as "holding tank" for new taxa until they would spread to the lower latitude. Similarly, Dettman (1989) observed that Antarctica was the cradle of austral temperate rainforests during the Cretaceous. These plants gradually migrated northwards during the Tertiary. The Antarctic fossil record contradicts the popular view that the tropics serve as the principal center for the origin and dispersal of biota; some groups of plants and animals apparently had polar origins during the Cretaceous and Early Tertiary period. Acknowledgments-We thank Bryan J. Small for field assistance, David G. Stahl for photography, and Kyle McQuilkin for computer graphics. The research was partly supported by the National Science Foundation (DPP 84-43487).

PY - 2003/1

Y1 - 2003/1

UR - http://www.scopus.com/inward/record.url?scp=0345474330&partnerID=8YFLogxK

U2 - 10.1671/0272-4634(2002)022[0848:ALCCCH]2.0.CO;2

DO - 10.1671/0272-4634(2002)022[0848:ALCCCH]2.0.CO;2

M3 - Article

AN - SCOPUS:0345474330

SN - 0272-4634

VL - 22

SP - 848

EP - 850

JO - Journal of Vertebrate Paleontology

JF - Journal of Vertebrate Paleontology

IS - 4

ER -