Climatically driven biogeographic provinces of Late Triassic tropical Pangea

Climatically driven biogeographic provinces of Late Triassic tropical Pangea

1. Jessica H. Whiteside (a,*),

2. Danielle S. Grogan (a)

3. Paul E. Olsen (b,*)

4. Dennis V. Kent (b,c)

a. Department of Geological Sciences, Brown University, 324 Brook Street, Box 1846, Providence, RI 02912;

b. Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964

c. Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854

*. To whom correspondence may be addressed. E-mail: Jessica_Whiteside@Brown.edu or polsen@ldeo.columbia.edu.

Abstract:

Although continents were coalesced into the single landmass Pangea, Late Triassic terrestrial tetrapod assemblages are surprisingly provincial. In eastern North America, we show that assemblages dominated by traversodont cynodonts are restricted to a humid 6° equatorial swath that persisted for over 20 million years characterized by “semiprecessional” (approximately 10,000-y) climatic fluctuations reflected in stable carbon isotopes and sedimentary facies in lacustrine strata. More arid regions from 5–20°N preserve procolophonid-dominated faunal assemblages associated with a much stronger expression of approximately 20,000-y climatic cycles. In the absence of geographic barriers, we hypothesize that these variations in the climatic expression of astronomical forcing produced latitudinal climatic zones that sorted terrestrial vertebrate taxa, perhaps by excretory physiology, into distinct biogeographic provinces tracking latitude, not geographic position, as the proto-North American plate translated northward. Although the early Mesozoic is usually assumed to be characterized by globally distributed land animal communities due to of a lack of geographic barriers, strong provinciality was actually the norm, and nearly global communities were present only after times of massive ecological disruptions.

ha! Called it! Over at Chineleana some time ago, I asked if anyone had looked at the difference in climates between the the American SW and the Newark Basin.

Note: SF Authors. If you have a supercontinent, its just as likely to have multiple ecosystems as a world broke up into multiple continents.

Another interesting note is that the procolophonids and the traversodont cynodonts seem to have been ecological equivalents. I don't know of any procs the size of Arctotraversodon though. It had a 40 cm skull, iirc.