44:
305:
is clearly given a place within an 'onchyophoran-like' clade, however, due to skin similarities to other 'onchyophoran-like' lobopodians and modern onchyophorans. These include bifurcating circumferential wrinkles, papillae mounted on solid bases, and (in parts) hexagonal patterning. This extends the
206:
preserved and much of the dorsal body surface missing. This missing surface was actually an advantage to the scientists studying it as it revealed the muscle fibres within the body. The skin has circumferential wrinkles spaced at 10 μm apart, which divide and merge irregularly. These wrinkles bear
245:
and part again near the outer edge of each lobopod, possibly for leg elevator muscle insertion. Inside this, there was a layer of much thinner, interwoven oblique fibres. The innermost layer of fibres is oriented perpendicular to the body axis, presumably the remains of a more extensive layer of
223:
The fossil found had two lobopods preserved, each around 800μm long and with a uniform diameter of 80μm, not tapering. At the end of each lobopod there are three 30μm claws preserved, with an angle of 45° between each one. The raised centres of the impressions of these claws denote a hollow claw
290:
However, the evolution of three-layered muscle from the two-layered muscle of more ancestral fossils is not straightforward. In living onchyophorans, the outermost layer of muscle is circular, the middle interwoven oblique and the innermost longitudinal, reversing the order of those in
254:
The preservation of the animal is unusual in several respects. Firstly, in Orsten-type microfossils muscle preservation is very rare and it is much more common that other tissue is preserved in phosphate in this way. Secondly, when onchyophorans are rotted in
240:
of the specimen, mostly making up the body wall. There were three layers of fibrous muscular tissue, each around 10μm thick. The outermost layer of muscle consisted of 5-10μm thick fibres, which part to leave a 60μm gap between the lobopods, thought to be a
275:
Previously, due to the rarity both of onchyophoran fossils and preserved musculature, it was uncertain whether peripheral muscle was a characteristic of all panarthropods or just of primitive
207:
small papillae which are thought to correspond to the dermal papillae of other extinct
Onchyophora. Along the two lobopods, the wrinkles become smaller and eventually give way to raised
224:
slightly longer than the 25μm impressions, hence the figure of 30μm. The lobopods had a circular cross-section, flattened in places, and are thought to be at the
158:. Its name loosely translates to "Three-clawed animal with well displayed flesh". Phylogenetic analysis suggests that it was a close relative of the
862:
867:
436:
842:
857:
267:
or the gut and before harder parts such as the hollow claws present in this species, of which only the inner bases remain.
215:
borders in the skin tissue. The papillae continue along the lobopods, with bases of around 5μm across and about 7μm high.
43:
852:
171:
847:
429:
283:(modern members of this clade have evolved skeletal muscle from the peripheral muscle in their ancestors).
199:
795:
287:
shows that peripheral muscle was also a feature of onchyophorans, and thus of panarthropods as a whole.
115:
177:
The muscle fibres preserved in its legs establish peripheral musculature as a characteristic of all
225:
837:
816:
684:
422:
296:
38:
162:, possibly even a member of the main lineage. The fossil was discovered in the Xiaotan section,
202:
of the animal found. This was 1 millimeter long, and folded at the mid-point, with one pair of
381:
260:
583:
371:
363:
228:
end of the specimen with the claws pointing towards the anterior, as in other lobopodians.
769:
652:
553:
507:
163:
733:
698:
624:
601:
500:
376:
351:
212:
831:
569:
521:
469:
178:
155:
783:
674:
659:
576:
562:
535:
514:
790:
740:
645:
631:
610:
237:
159:
78:
691:
638:
617:
528:
280:
147:
263:, body wall muscles are the first parts to decay, well before organs such as
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716:
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463:
445:
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55:
385:
367:
776:
747:
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542:
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400:
311:
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30:
310:, along with the multiple layers of peripheral muscle and the possible
208:
493:
457:
352:"Onychophoran-like musculature in a phosphatized Cambrian lobopodian"
195:
167:
151:
65:
264:
418:
401:"World's oldest muscle-fibre fossil reveals the origin of legs"
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181:, but are arranged in an unusual pattern (detailed below).
154:
fashion by phosphate deposition, additionally preserving
350:
Zhang XG, Smith MR, Yang J, Hou JB (September 2016).
809:
757:
715:
673:
600:
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478:
430:
8:
345:
343:
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299:of muscle layers unclear, to say the least.
236:The muscles preserved were those inside the
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549:
437:
423:
415:
20:
375:
306:record of these features into the lower
323:
7:
16:Extinct species of Cambrian organism
14:
150:, exceptionally preserved in the
42:
198:found was small, with only one
399:Kezzei A (28 September 2016).
1:
863:Fossil taxa described in 2016
211:boundaries, which could mark
884:
868:Cambrian genus extinctions
452:
285:Tritonychus phanerosarkus
143:Tritonychus phanerosarkus
128:Tritonychus phanerosarkus
121:
114:
39:Scientific classification
37:
23:
843:Cambrian animals of Asia
271:Evolutionary importance
858:Paleontology in Yunnan
368:10.1098/rsbl.2016.0492
134:Zhang & Smith 2016
107:T. phanerosarkus
172:Yu'anshan Formation
817:Category:Lobopodia
810:Related categories
760:Gilled lobopodians
685:Antennacanthopodia
479:Controversial taxa
246:circular muscles.
825:
824:
805:
804:
669:
668:
190:External features
139:
138:
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853:Fossils of China
755:
584:Rhombocorniculum
550:
439:
432:
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416:
409:
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405:The Conversation
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295:This leaves the
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29:Temporal range:
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883:
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873:
872:
828:
827:
826:
821:
801:
770:Kerygmachelidae
753:
711:
665:
653:Miraluolishania
596:
554:Hallucigeniidae
548:
508:Lenisambulatrix
474:
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362:(9): 20160492.
356:Biology Letters
349:
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261:saline solution
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168:Yunnan Province
135:
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41:
33:
27:
17:
12:
11:
5:
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848:Cambrian China
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734:Jianshanopodia
730:
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699:Orstenotubulus
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602:Luolishaniidae
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501:Fusuconcharium
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146:is a Cambrian
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724:
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721:
719:-related taxa
718:
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677:-related taxa
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570:Cardiodictyon
567:
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555:
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545:
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522:Onychodictyon
519:
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470:Panarthropoda
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462:Superphylum:
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179:panarthropods
175:
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156:muscle fibres
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116:Binomial name
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26:
22:
19:
796:Dinocaridida
789:
784:Pambdelurion
782:
775:
768:
746:
739:
732:
725:
705:
704:
697:
690:
683:
675:Onychophoran
660:Ovatiovermis
658:
651:
644:
637:
630:
623:
616:
609:
589:
582:
577:Hallucigenia
575:
568:
563:Carbotubulus
561:
541:
536:Quadratapora
534:
527:
520:
515:Microdictyon
513:
506:
499:
492:
485:
404:
394:
359:
355:
302:
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293:Tritonychus.
292:
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277:euarthropods
274:
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250:Preservation
235:
222:
193:
176:
142:
141:
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127:
122:
106:
105:
92:
91:
72:
24:
18:
791:Opabiniidae
741:Megadictyon
706:Tritonychus
646:Luolishania
632:Entothyreos
611:Acinocricus
446:Lobopodians
303:Tritonychus
281:tardigrades
238:body cavity
232:Musculature
160:Onychophora
93:Tritonychus
79:Onychophora
25:Tritonychus
832:Categories
794:(Also see
692:Helenodora
639:Facivermis
618:Collinsium
529:Paucipodia
318:References
219:Appendages
148:lobopodian
73:Stem group
838:Lobopodia
717:Arthropod
591:Thanahita
464:Ecdysozoa
456:Kingdom:
226:posterior
209:polygonal
100:Species:
62:Kingdom:
56:Eukaryota
777:Omnidens
748:Siberion
727:Hadranax
543:Xenusion
487:Aysheaia
458:Animalia
386:27677816
312:gonopore
308:Cambrian
297:homology
257:seawater
243:gonopore
204:lobopods
185:Features
164:Yongshan
66:Animalia
52:Domain:
31:Cambrian
468:Clade:
377:5046927
200:segment
170:in the
125:†
104:†
85:Genus:
494:Diania
384:
374:
265:gonads
196:fossil
152:Orsten
382:PMID
279:and
213:cell
194:The
372:PMC
364:doi
259:or
834::
403:.
380:.
370:.
360:12
358:.
354:.
326:^
314:.
174:.
166:,
75::
798:)
762:"
758:"
438:e
431:t
424:v
407:.
388:.
366::
89:†
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