Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Toward an understanding of cosmopolitanism in deep time; a case study of ammonoids from the Middle Permian to the Middle Triassic

Dai Xu and Song Haijun
Toward an understanding of cosmopolitanism in deep time; a case study of ammonoids from the Middle Permian to the Middle Triassic
Paleobiology (November 2020) 46 (4): 533-549

Abstract

Cosmopolitanism occurred recurrently during the geologic past, especially after mass extinctions, but the underlying mechanisms remain poorly known. Three theoretical models, not mutually exclusive, can lead to cosmopolitanism: (1) selective extinction in endemic taxa, (2) endemic taxa becoming cosmopolitan after the extinction and (3) an increase in the number of newly originated cosmopolitan taxa after extinction. We analyzed an updated occurrence dataset including 831 middle Permian to Middle Triassic ammonoid genera and used two network methods to distinguish major episodes of ammonoid cosmopolitanism during this time interval. Then, we tested the three proposed models in these case studies. Our results confirm that at least two remarkable cosmopolitanism events occurred after the Permian-Triassic and late Smithian (Early Triassic) extinctions, respectively. Partitioned analyses of survivors and newcomers revealed that the immediate cosmopolitanism event (Griesbachian) after the Permian-Triassic event can be attributed to endemic genera becoming cosmopolitan (model 2) and an increase in the number of newly originated cosmopolitan genera after the extinction (model 3). Late Smithian cosmopolitanism is caused by selective extinction in endemic taxa (model 1) and an increase in the number of newly originated cosmopolitan genera (model 3). We found that the survivors of the Permian-Triassic mass extinction did not show a wider geographic range, suggesting that this mass extinction is nonselective among the biogeographic ranges, while late Smithian survivors exhibit a wide geographic range, indicating selective survivorship among cosmopolitan genera. These successive cosmopolitanism events during severe extinctions are associated with marked environmental upheavals such as rapid climate changes and oceanic anoxic events, suggesting that environmental fluctuations play a significant role in cosmopolitanism.


ISSN: 0094-8373
EISSN: 1938-5331
Coden: PALBBM
Serial Title: Paleobiology
Serial Volume: 46
Serial Issue: 4
Title: Toward an understanding of cosmopolitanism in deep time; a case study of ammonoids from the Middle Permian to the Middle Triassic
Author(s): Dai XuSong Haijun
Affiliation: China University of Geosciences-Wuhan, State Key Laboratory of Biogeology and Environmental Geology, Wuhan, China
Pages: 533-549
Published: 202011
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 99
Accession Number: 2021-003292
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2021
Close Modal

or Create an Account

Close Modal
Close Modal