Agnostida from the Late Cambrian of Guole, Guangxi

[oilshale]

Hi everyone,

I recently got this small Agnostida from the Late Cambrian (Sandu Formation) of Guole, Guangxi PRC. I have no idea to what species this little "two-headed" bugger belongs. Anyone can help?

Thanks

Thomas

[JohnBrewer]

That's a fabulous looking bug Thomas. 

 

@piranha @Arizona Chris 

[piranha]

Rhaptagnostus cf. clarki maximus 

 

figures from:

 

Zhu, X.J. (2005)

Trilobite Faunas from Cambrian Upper Furongian of Guangxi with special notes on malformation, dimorphism, and function of eye ridges.

PhD Thesis, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 224 pp.

 

 

[Malcolmt]

That bug is definitely a little keeper. Sure seems to be a match with Scott's identification

 

[RJB]

Cool lookin little bugger! 

 

RB

[Haravex]

Piranha well spotted in the identification and yes definitely a keeper I have never seen one of these before. 

[Sagebrush Steve]

So to my untrained eye this looks just like the Peronopsis species from the Wheeler shale in Utah (they are apparently also found in Asia).  Can someone explain the difference, as this one doesn't appear to even be in the same genus.  Its definitely a keeper, though!

[Douvilleiceras]

34 minutes ago, Sagebrush Steve said:

So to my untrained eye this looks just like the Peronopsis species from the Wheeler shale in Utah (they are apparently also found in Asia).  Can someone explain the difference, as this one doesn't appear to even be in the same genus.  Its definitely a keeper, though!

They look similar as possessing only a few body segments and having a nearly isopygous outline is a characteristic of the Order Agnostida. This particular specimen (as well as Itagnostus interstrictus  - the new name for Peronopsis interstricta) are both members of the Suborder Agnostina, which is distinguished from its fellow Suborder Eodiscina by the latter's presence of eyes, sutures, and up to three body segments (versus only two in Agnostina). While they are in different families, they are still in the same superfamily: the Agnostoidea.

 

However, there are some significant differences. These differences between the genus Rhaptagnostus and Itagnostus include effacement (loss of detail) on the former, resulting in a trilobite lacking the clearer segments and pronounced glabella of Itagnostus.

[piranha]

4 hours ago, Sagebrush Steve said:

So to my untrained eye this looks just like the Peronopsis species from the Wheeler shale in Utah (they are apparently also found in Asia).  Can someone explain the difference, as this one doesn't appear to even be in the same genus.  Its definitely a keeper, though!

 

 

Peronopsis (=Itagnostus) is Middle Cambrian. There are 4 agnostids in the Upper Cambrian Guole biota: Lotagnostus, Micragnostus, Neoagnostus, Rhaptagnostus

 

Here are the descriptions from the Treatise on Invertebrate Paleontology, Part O Revised 1997:

 

Peronopsis HAWLE & CORDA, 1847, p. 115 [*Battus integer BEYRICH, 1845, p. 44; OD; lectotype (PEK & VANEK, 1971, p. 270, pl. 1, fig. 6), Beyrich Collection 86(530), HMB, Berlin] [=Mesospheniscus HAWLE & CORDA, 1847, p. 46 (type, M. cuneifer; OD); Mesagnostus JAEKEL, 1909, p. 397 (type, Battus interger BEYRICH, 1845, p. 44, fig. 19)]. Nonscrobiculate; narrow border in cephalon and wide, flat border in pygidium; median preglabellar furrow absent. Glabella with subquadrate to semiovate anterior lobe; posterior lobe with glabellar node a short distance behind F2. Pygidium nonspinose or bispinose; axis strongly convex, broadly ogival; F1 weak; F2 weak or absent, straight; posterior lobe broadly ogival, narrowly rounded to acuminate posteriorly, with a weakly developed transverse depression at about midlength. Middle Cambrian: ?Sweden; Czech Republic, P. (P.) gracilis Zone.——FIG. 229,1a,b. *P. integra (BEYRICH), Middle Cambrian (Paradoxides gracilis Zone), Czech Republic (Jince, Bohemia); a, topotype, exoskeleton, SBNM Br-190/56, ×10 (Horny & Bastl, 1970); b, lectotype, pygidium, HMB Beyrich Collection 86(530), ×10.7 (Pek & Vanek, 1971, pl. 1, fig. 6–7).

 

Rhaptagnostus WHITEHOUSE, 1936, p. 97 [*Agnostus cyclopygeformis Y. SUN, 1924, p. 26; OD; lectotype (Y. SUN, 1924, pl. 2, fig. 1e), 507, NIGP, Nanjing]. Characteristically with subovoid to subcircular cephalon and pygidium; effaced to partly effaced; with nondeliquiate border furrows. Cephalon papilionate, with effaced median preglabellar furrow. Pygidium variably deuterolobate, with weakly constricted acrolobe; marginal spines well in advance of rear of deuterolobe. Upper Cambrian: Australia (Queensland), W. iota or R. apsis to N. quasibilobus or S. nomas Zones; China (Anhui, Hebei, Liaoning, Shandong, Yunnan, Qinghai, Xinjiang), Kaolishania to Tsinania Zones, (Zhejiang), L. punctatus Zone, (Guizhou), zone uncertain; North and South Korea, Fengshanian, Tsinania to Eoorthis Zones; Kazakhstan, E. scrobicularis to T. trisulcus Zones, Russia (Yakutia), P. perlata Zone; Canada (Northwest Territories, Newfoundland), Yukonaspis Zone; USA (Alaska, Montana, Nevada, Vermont), S. pyrene to S. serotina Subzones; Mexico, pre-Cordylodus proavus Zone.— FIG. 233,3a. *R. cyclopygeformis (SUN), Upper Cambrian (Changshanian, Kaolishania Zone), China (Kaolishan, Taian, Shandong); lectotype, pygidium, NIGP 507, ×7 (X. Sun, 1989, pl. 5, fig. 10).——FIG. 233,3b,c. R. convergens (PALMER), Upper Cambrian (Trempealeauan, Saukiella pyrene Subzone), USA (Eureka district, Nevada); b, paratype, cephalon, USNM 123563, ×10; c, holotype, pygidium, USNM 123562, ×9.5 (Shergold, 1977).

[oilshale]

2 hours ago, piranha said:

Rhaptagnostus cf. clarki maximus 

 

figures from:

 

Zhu, X.J. (2005)

Trilobite Faunas from Cambrian Upper Furongian of Guangxi with special notes on malformation, dimorphism, and function of eye ridges.

PhD Thesis, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 224 pp.

 

 

 

I am sort of speechless: After several hours unsuccessfully trying to find out what species this little bug is, I finally gave up and you nailed it down in no time! 

Hats off and thanks a lot

Thomas

[doushantuo]

Scott,does the English summary of that thesis contain the species descriptions?

[piranha]

1 hour ago, doushantuo said:

...does the English summary of that thesis contain the species descriptions?

 

 

Yes, but not Rhaptagnostus cf. clarki maximus.  The English summary only has descriptions of new genera and species.

 

 

Here is the original description: Pseudagnostus clarki maximus Shergold 1975

It was subsequently reclassified: Rhaptagnostus clarki maximus Shergold 1977

 

PSEUDAGNOSTUS CLARKI Kobayashi, 1935, MAXIMUS subsp. nov.

Diagnosis: A subspecies of Pseudagnostus clarki with its maximum cephalic width (tr.) lying on a transverse line through the centre of the axial glabellar node, and its maximum pygidial width (tr.) lying to the rear of the third axial metamer. Differential diagnosis: This subspecies is differentiated from others referred to Pseudagnostus clarki on the shape of its shields alone (Tables 1 and 2). In all other characteristics-proportions, positions of nodes, spines, and borders-it is similar to P. clarki patulus. Description of external testaceous surfaces: P. clarki  maximus is proportionately very similar to P. c. patulus, and the subspecies are effaced to similar degrees. The description of patulus thus serves also for maximus, except for the shape of the shields. As indicated in the diagnosis the cephalon is widest (tr.) at the level of the axial node, and the pygidium at the rear of the third metamer. Description of the parietal surfaces: The parietal surfaces of Pseudagnostus clarki maximus have identical distribution and orientation of muscle scars with those of P. c. patulus and P. c. prolatus. In the cephalon the axial glabellar sulcus is better defined and wider, showing a situation closely resembling that of the intranotular sulcus of the pygidium. As in clarki patulus notular pits are observed within the oblique lateral scars of the posterior glabellar lobe. The caecal network is not well preserved, but the visible parts are very closely comparable with corresponding parts of the system of P. c. prolatus. In the pygidium the arrangement of the muscle scars and notulae again compares to the situation observed in clarki patulus. There are traces of eleven metameres, those to the rear of the defined axis having readily visible duplicated notulae on each segment (PI. 5, fig. 2). The caecal network of the pygidium is not well preserved.

 

Shergold, J.H. (1975)
Late Cambrian and Early Ordovician Trilobites from the Burke River Structural Belt, Western Queensland, Australia.
Australia Bureau of Mineral Resources, Geology and Geophysics Bulletin,  153:1-251 PDF TEXT   153:1-119 PDF PLATES

 

Shergold, J.H. (1977)
Classification of the Trilobite Pseudagnostus. 
Palaeontology, 20(1):69-100    PDF LINK