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Article: Saccoglossus testa from the Mazon Creek fauna (Pennsylvanian of Illinois) and the evolution of acorn worms (Enteropneusta: Hemichordata)

Palaeontology Cover Image - Volume 59 Part 3
Publication: Palaeontology
Volume: 59
Part: 3
Publication Date: May 2016
Page(s): 329 336
Author(s): Christopher B. Cameron
Addition Information

How to Cite

CAMERON, C.B. 2016. Saccoglossus testa from the Mazon Creek fauna (Pennsylvanian of Illinois) and the evolution of acorn worms (Enteropneusta: Hemichordata). Palaeontology, 59, 3, 329-336. DOI: 10.1111/pala.12235

Author Information

  • Christopher B. Cameron - Université de Montréal Département de Sciences Biologiques Montréal Quebec Canada (Email: c.cameron@umontreal.ca)

Publication History

  • Issue published online: 19 April 2016
  • Article first published online: 01 January 1970
  • Manuscript Accepted: 11 February 2016
  • Manuscript Received: 29 December 2015

Funded By

Natural Sciences and Engineering Research Council of Canada (NSERC)

Online Version Hosted By

Wiley Online Library (Free Access)
Get Article: Wiley Online Library [Free Access]

Abstract

The limited fossil record of enteropneust hemichordates (acorn worms) and the few external features that distinguish the four families have provided a challenge to our understanding of the evolution of the group and their various feeding adaptations. The middle Pennsylvanian Saccoglossus testa sp. nov. from the Mazon Creek, Westfalian D Carbonate Formation, Francis Creek Shale of northern Illinois provides evidence for the exploitation of surface sediments. Saccoglossus testa has a long proboscis characteristic of the extant genus Saccoglossus, a specialist in surface deposit feeding. The collar is as long as it is wide. The anterior trunk lacks a distinctively wide branchial region. These three features distinguish it from its sympatric enteropneust species Mazoglossus ramsdelli Bardack that has a proboscis characteristic of an infaunal deposit feeder. It is the seventh known species of fossil enteropneust, including a resting trace of a Lower Triassic fossil that has collar lips that characterize the extant deep‐sea family Torquaratoridae, and which represents a second parallel evolution of surface deposit feeding. An analysis of the seven fossils shows that the earliest Enteropneusta had a relatively simple harrimaniid‐like body plan, and that the spengelid, the torquaratorid and lastly the most complex ptychoderid body plan appeared in that chronological order.

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