Trilobitas tinham estômago, contrariando prévias pressuposições sobre sua evolução e o sistema digestivo

sexta-feira, setembro 22, 2017

The oldest known digestive system consisting of both paired digestive glands and a crop from exceptionally preserved trilobites of the Guanshan Biota (Early Cambrian, China)

Melanie J. Hopkins , Feiyang Chen, Shixue Hu, Zhifei Zhang 

Published: September 21, 2017


The early Cambrian Guanshan biota of eastern Yunnan, China, contains exceptionally preserved animals and algae. Most diverse and abundant are the arthropods, of which there are at least 11 species of trilobites represented by numerous specimens. Many trilobite specimens show soft-body preservation via iron oxide pseudomorphs of pyrite replacement. Here we describe digestive structures from two species of trilobite, Palaeolenus lantenoisi and Redlichia mansuyi. Multiple specimens of both species contain the preserved remains of an expanded stomach region (a “crop”) under the glabella, a structure which has not been observed in trilobites this old, despite numerous examples of trilobite gut traces from other Cambrian Lagerstätten. In addition, at least one specimen of Palaeolenus lantenoisi shows the preservation of an unusual combination of digestive structures: a crop and paired digestive glands along the alimentary tract. This combination of digestive structures has also never been observed in trilobites this old, and is rare in general, with prior evidence of it from one juvenile trilobite specimen from the late Cambrian Orsten fauna of Sweden and possibly one adult trilobite specimen from the Early Ordovician Fezouata Lagerstätte. The variation in the fidelity of preservation of digestive structures within and across different Lagerstätten may be due to variation in the type, quality, and point of digestion of food among specimens in addition to differences in mode of preservation. The presence and combination of these digestive features in the Guanshan trilobites contradicts current models of how the trilobite digestive system was structured and evolved over time. Most notably, the crop is not a derived structure as previously proposed, although it is possible that the relative size of the crop increased over the evolutionary history of the clade.

Citation: Hopkins MJ, Chen F, Hu S, Zhang Z (2017) The oldest known digestive system consisting of both paired digestive glands and a crop from exceptionally preserved trilobites of the Guanshan Biota (Early Cambrian, China). PLoS ONE 12(9): e0184982.

Editor: Steffen Kiel, Naturhistoriska riksmuseet, SWEDEN
Received: April 17, 2017; Accepted: September 4, 2017; Published: September 21, 2017

Copyright: © 2017 Hopkins et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting Information files.

Funding: Fossil collection was partly financed by the National 973 Program (2013CB835002) and 111 Project of China (P201102007). This work represents a contribution to the research programmes from the National Natural Science Foundation of China (NSFC 41425008 and 41621003 to ZZ). The funders had no role in the study design, data collections and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.