Mongolitubulus Missarzhevsky, 1977

Wrona, Ryszard, 2004, Cambrian microfossils from glacial erratics of King George Island, Antarctica, Acta Palaeontologica Polonica 49 (1), pp. 13-56 : 42

Genus Mongolitubulus Missarzhevsky, 1977

Type species: Mongolitubulus squamifer Missarzhevsky, 1977 .

Emended diagnosis.—Minute phosphatic spines, straight to slightly arched, covered with distinct rhomboid scale−like ornamentation. Rhomboids are sharp or rounded, inclined away from the spine wall in direction of apex, and arranged in alternating rows. Spine wall bilayered; outer layer is dense or hyaline and structureless, inner layer consists of longitudinal fibres parallel to spine axis. Large internal cavity ocuppies almost entire length of the spine.

Species included.—All species are known as isolated and incomplete spines: Mongolitubulus squamifer Missarzhevsky, 1977 ; Mongolitubulus ex gr. M. squamifer Missarzhevsky (Demidenko in Gravestock et al. 2001: 87, pl. 11: 5); M. henrikseni Skovsted and Peel, 2001 .

Remarks.—The problematic microfossil Mongolitubulus was first reported and has been known for a long time as incomplete, 1–2mm long tubes, later described as hollow spines ( Wrona 1989). Recently recovered abundant and more complete specimens from Greenland ( Skovsted and Peel 2001) show that they represent only part of a larger skeletal elements or spiny sclerites of the multielement scleritome of a still enigmatic animal. Dzik (2003), analysing Mongolitubulus spine morphology and internal structure as well as the whole range of the associated fossil assemblage, in particular the Microdictyon component, believed that they protected the body of a lobopodian−like animal similar to Xenusion . Some ornamented tubes (Conway Morris and Bengtson in Bengtson et al. 1990: 158, figs. 102and 103), often referred to the pseudo − conodont Rhombocorniculum ( Brasier 1986: 253; Landing 1988: 687) or Rushtonites ( Hinz 1987: 74) , and having virtually the same distinct internal structure and external morphology, are comparable to Mongolitubulus , and judging from the new material described by Skovsted and Peel (2001), they could be certainly referred to this genus.