Mongolitubulus

Mongolitubulus Temporal range: Lower Cambrian–Early Middle Cambrian[1] PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
stem group:	Crustacea
Order:	†Bradoriida
Genus:	†Mongolitubulus Missarzhevsky, 1977
Species
M. henrikseni Skovsted & Peel, 2001 M. squamifer Missarzhevsky, 1977 (type)
Synonyms
Rushtonites Hinz 1987

Mongolitubulus is a genus of small shelly fossil. It is potentially a synonym with Rushtonites, and owing to the similarity of the two genera^[1] they are both dealt with herein.

Morphology

The fossils consist of round, slender, pointed, spines with a slight curvature, and are covered with short triangular processes.^[1] Spines very from sub-millimetric up to two centimetres in length, but do not show any growth lines, suggesting that they were moulted and replaced.^[2] Species are defined on the basis of the ornamentation, which may of course be convergent.

Affinity

M. henrikseni has been shown to be part of the carapace of a bivalved bradoriid arthropod.^[3] However, the affinity of M. squamifer is still unresolved; the genus may transpire to be a form taxon, which would require M. henrikseni to be re-classified into a new genus.^[3] Unlike the spines of M. henrikseni, which flare out at the base where they attach to the cuticle, the spines of M. squamifer are more parallel-sided, with the fossil material becoming thinner towards the base: consistent with their attachment to non-mineralized cuticle.^[2] M. squamifer spines appear to have formed in pairs, owing to their symmetry; on this basis they have been likened to the spines of certain armoured lobopods known from Burgess shale-type deposits.^[2]

Preservation

The spines often comprise layers of phosphate, with a central void often infilled with diagenetic phosphate.^[2] Similar spines have been recovered from acid macerations, where they are preserved as films of organic carbon.^[4]

Distribution

The fossils are known from the Botomian to the lower strata of the Middle Cambrian,^[1] and have a worldwide distribution.^[2]

References

1. ^ ^{a b c d} Skovsted, C. E.; Peel, J. S. (2001). http://2dgf.dk/xpdf/bull48-2-135-147.pdf. 
2. ^ ^{a b c d e} Dzik, J. (2003). "Early Cambrian lobopodian sclerites and associated fossils from Kazakhstan". Palaeontology 46: 93. doi:10.1111/1475-4983.00289. http://www.paleo.pan.pl/people/Dzik/Publications/Mongolitubulus.pdf.  edit
3. ^ ^{a b} Skovsted, C. (2005). "A carapace of the bradoriid arthropod Mongolitubulus from the Early Cambrian of Greenland". GFF 127: 217. doi:10.1080/11035890501273217.  edit
4. ^ Butterfield, N. J.; Nicholas, C. J. (1996). "Burgess Shale-Type Preservation of Both Non-Mineralizing and 'Shelly' Cambrian Organisms from the Mackenzie Mountains, Northwestern Canada". Journal of Paleontology 70 (6): 893–899. JSTOR 1306492.  edit