Earliest Onychophoran in Amber Reveals Gondwanan Migration Patterns.
The anomalous occurrence of supposedly Gondwanan taxa in Laurasian-derived regions remains an intriguing chapter of paleobiogeographical history. Representatives of Peripatidae, a major subgroup of velvet worms (Onychophora), show a disjointed distribution in the neotropics, tropical Africa, and Southeast Asia, the latter being the only landmass previously associated with Laurasia [1, 2]. The arrival of these animals in Southeast Asia is explained by two alternative, albeit not mutually exclusive, hypotheses: an early migration via Europe before continental drift (Eurogondwana hypothesis) or transportation via insular India during the Cretaceous and Paleogene ("out-of-India" hypothesis) [3-6]. The latter hypothesis is based on a single extant species of Peripatidae, Typhloperipatus williamsoni, in India. †Cretoperipatus burmiticus from Myanmar is the oldest fossil onychophoran found in amber [7], dating to sometime between the two proposed scenarios, and hence crucial for clarifying how Gondwanan lineages of these low-vagility animals reached Southeast Asia (see also Supplemental Information). Based on the anatomical reconstruction of †C. burmiticus using synchrotron radiation-based X-ray microtomography (SRμCT) and comparisons with extant taxa, we resolved this fossil species within Onychophora, particularly within Peripatidae, with T. williamsoni as its closest extant relative. This suggests that an early Eurogondwanan migration of peripatids was the most likely event, as Burmese amber is too old to be compatible with the out-of-India hypothesis. Moreover, peripatids probably colonized India only recently from Myanmar, refuting the putative Gondwanan relict status of Indian onychophorans. Finally, preservation artifacts identified in the novel amber material might have a major impact on studies of onychophoran stem and/or crown groups.
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Box 92, Beichen West Road 1, Chaoyang District, 100101 Beijing, China; Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany. Electronic address: ivo.oliveira@uni-kassel.de.
Ivo de Sena
IS
Oliveira
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Box 92, Beichen West Road 1, Chaoyang District, 100101 Beijing, China. Electronic address: baim@ioz.ac.cn.
Ming
M
Bai
Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany.
Henry
H
Jahn
Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany.
Vladimir
V
Gross
Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany.
Christine
C
Martin
Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, Germany.
Jörg U
JU
Hammel
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Box 92, Beichen West Road 1, Chaoyang District, 100101 Beijing, China.
Weiwei
W
Zhang
Department of Zoology, Institute of Biology, University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany.
Georg
G
Mayer
D018647:Amber; D063147:Animal Distribution; D000818:Animals; D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology*; D007448:Invertebrates / Q000033:anatomy & histology* / Q000145:classification* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D002052:Myanmar; D010802:Phylogeny; D055114:X-Ray Microtomography
D018647:Amber
Cretaceous; Onychophora; Peripatidae; SRμCT; Southeast Asia; amber; biogeography; fossil; velvet worm