The first ocurrence of the genus Tonkinella Mansuy,1916 in the Spanish Middle Cambrian  

GozALo R., MAYORAL E. , GÁMEZ VINTANED J. A.  AND DIES M. E.

The genus Tonkinella Mansuy, 1916 is a typical polimeroid trilobite in early Middle Cambrian rocks from Vietnam, Canada, U.S.A., India, Korea, Siberia and China. Here we refer a new finding of T. aff. breviceps Kobayashi, 1934 in the early Middle Cambrian of the Cantabrian Mountams (northern Spain).

The fossil studied herein has been recovered from the lowermost visible strata of the Oville Formation at the Presa del Porma section named "Pu" (León province). Tonkinella aff. breviceps has been found in the same level where the following trilobites species appear: Eccaparadoxides asturianus (Sdzuy, 1968), Paradoxides? enormis Sdzuy, 1968, Acadolenus decorus Sdzuy, 1968 and Conocoryphe (Parabailiella) matutina Sdzuy, 1968. The age of this assemblage is E. asturianus zone, which characterises the Upper Leonian in the Mediterranean biochronólogy. An Upper Leonian age for the specimens of T. aff. breviceps cited herein is also supported by the first record of Badulesia tenera (Hartt in Dawson, 1865), which is placed some 4 m above in the same succession. The FAD of this species marks the beginning of the Caesaraugustan Stage. The Leonian/Caesaraugustan boundary has been correlated with the base of Triplagnostus gibbus zone by Sdzuy et al. (1999).

For the moment, the most continuous record of Tonkinella has been found in the Great Basin of North America by Sundberg (1994). T. breviceps appears in the Altiocculus subzone (uppermost Ehmaniella zone) defined by Sundberg (op. cit.), and the findings of this species from other countries are of a similar age (Sundberg, 1994; Jell & Hughes, 1997). The level containing T. aff. breviceps in Spain can be correlated with a level just below the FAD of Triplagnostus gibbus.  

In consequence, we correlate tentatively the level with T. aff. breticeps with the lower part of Altiocculus subzone, particularly with the levels previous to the T. gibbus FAD.  

Ackowledgements. We wish to thank Prof. Eladio Liñán for suggestions about the text. We acknowledge support from the Dirección General de Enseñanza Superior, Project PB96-0744. M. E. Dies enjoys a predoctoral research grant from the Diputación General de Aragón.  

References  

Jell, P. A. and Hughes, N. C. 1997. Himalayan Cambrian Trilobites. Special Papers in Palaeontology 58, 1-113.

Sdzuy, K., Liñán, E. and Gozalo, R. 1999. The Leonian Stage (early Middle Cambrian): a unit for Cambrian correlation in the Mediterranean subprovince. GeologicalMagazine 136 (1),39-48. 

Sundberg, E A. 1994. Corynexochida and Ptychopariida (Trilobita, Arthropoda) of the Ehmaniella Biozone (Middle Cambrian), Utah and Nevada. Contributions in Science. Natural History Museum of Los Angeles County 446, 1-137.