Morphology, biostratigraphy, and evolution of Pliocene-Pleistocene diatoms Proboscia barboi and Proboscia curvirostris

Authors

  • J.P. Andrade Departamento de Ciências da Terra, Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
  • P. Legoinha Geobiotec, Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
  • Z. Stroynowski Marine Geology Division, IPMA (Instituto Português do Mar e da Atmosfera) Rua Alfredo Magalhães Ramalho 6, 1495-006 Algés, Portugal CCMAR (Centro de Ciências do Mar do Algarve) Universidade do Algarve, 8005-139, Faro, Portugal
  • F. Abrantes Marine Geology Division, IPMA (Instituto Português do Mar e da Atmosfera) Rua Alfredo Magalhães Ramalho 6, 1495-006 Algés, Portugal CCMAR (Centro de Ciências do Mar do Algarve) Universidade do Algarve, 8005-139, Faro, Portugal

Keywords:

Probosciaceae, Proboscis, Longitudinal ridges, Site U1340, Quaternary

Abstract

Proboscia barboi and Proboscia curvirostris are two important diatom biostratigraphic markers from the high latitudes of the North Pacific and North Atlantic Oceans, dating back to the Pliocene-Pleistocene time. This study analyzes the biostratigraphic events and describes the morphology of P. barboi and P. curvirostris, particularly the morphologic variations of the latter species, based on observations of samples of Core U1340A from the IODP Expedition 323 in the Bering Sea. In Site U1340, the First Occurrence of P. curvirostris is observed at 1.52Ma and its First Common Occurrence at 1.39Ma, where morphologic variations were found abundantly. The Last Occurrence of P. curvirostris was found at 0.33Ma, while P. barboi’s Last Occurrence is found at 0.67Ma. Based on the morphological similarity and known biostratigraphic distribution, previous authors have assumed that P. curvirostris descends from P. barboi, although this hypothesis is still in debate. At 1.39Ma P. curvirostris shows an increased size and thickness, which is typical of P. barboi, and some specimens display an incipient structure characteristic of P. curvirostris - the secondary spine. This morphology is intermediate between the two species and suggests an evolutionary transition from P. barboi to P. curvirostris. However, P. curvirostris already existed since 1.9Ma in the subarctic indicating that its speciation happened much earlier than 1.39Ma. Furthermore, since P. barboi co-occurs with P. curvirostris in the North Pacific, this evolutionary process was cladogenetic. Besides being evidence for a phylogenetic relationship, the abundant occurrence of intermediate forms at 1.39Ma may constitute a bioevent for a short time interval in the Bering Sea.

Author Biographies

P. Legoinha, Geobiotec, Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa, 2829-516 Caparica, Portugal

Departamento de Ciências da Terra

F. Abrantes, Marine Geology Division, IPMA (Instituto Português do Mar e da Atmosfera) Rua Alfredo Magalhães Ramalho 6, 1495-006 Algés, Portugal CCMAR (Centro de Ciências do Mar do Algarve) Universidade do Algarve, 8005-139, Faro, Portugal

Marine Geology Division

Downloads

Published

2019-10-21

Issue

Section

Articles