02595nas a2200217 4500008004100000245012600041210006900167300001200236490000700248520192800255653001402183653002802197653001102225653001502236653001902251100001502270700001802285700001602303700001902319856003902338 2011 eng d00aLinguliform Brachiopods from the Terminal Cambrian and Lowest Ordovician of the Oaxaquia Microcontinent (Southern Mexico)0 aLinguliform Brachiopods from the Terminal Cambrian and Lowest Or a122-1550 v853 a

Eighteen taxa of linguliform brachiopods, mainly represented by acrotretoids, are reported from the Upper Cambrian (Furongian, Stage 10) and Lower Ordovician (Tremadocian) Tiñu Formation of Oaxaca State, Mexico. At the time of deposition, this area was part of Oaxaquia, which was either a microcontinent or an integral part of the Gondwanan margin. Whereas certain trilobites seem to indicate a Gondwanan affinity, the Tiñu brachiopod faunas show a less definite paleogeographic relationship. Some taxa have previously only been reported from Laurentia (Eurytreta cf. fillmorensis, Eurytreta cf. campaniformis), and one taxon is best known from the Avalon microcontinent (Eurytreta cf. sabrinae). However, the relatively high percentage of new and potentially endemic taxa (Oaxaquiatreta labrifera n. gen. n. sp., Tapuritreta reclinata n. sp., Oaxaquiatreta sp., Eurytreta? n. sp., Acrotretidae n. gen. n. sp., Obolinae gen. and sp. indet.) and the lack of other typical Laurentian, Gondwanan, or Avalonian taxa suggest either a certain degree of insularity of Oaxaquia or reflects a more temperate, unrestricted marine environment during the Early Paleozoic. Other taxa reported from the Tiñu Formation include Semitreta sp., Lingulella? spp., Obolinae gen. and sp. indet., Eoscaphelasma? sp., Ottenbyella? sp. A and sp. B, and Acrotretidae gen. and sp. indet. A, B, and C. Eurytreta and Semitreta are critically reviewed and several taxa previously assigned to them have been excluded. An emended diagnosis for the genus Eurytreta is presented. The presence of delthyrium and notothyrium-like structures in the siphonotretid Oaxaquiatreta n. gen. further strengthens the previously proposed relationship between the Siphonotretida and Paterinida.

10aEurytreta10aLinguliform brachiopods10aMexico10aPaterinida10aSiphonotretida1 aStreng, M.1 aMelbin, B., B1 aLanding, E.1 aKeppie, J., D. uhttp://dx.doi.org/10.1666/10-074.1