LOWER PERMIAN PERRINITID AMMONOID FAUNAS FROM THAILAND

Journal of Paleontology, Mar 2004 by Zhou, Zuren, Liengjarern, Malai

As extra biostratigraphic evidence, the following fusulinids were identified primarily from beds KNH1-KNH4 of the Perrinites-ammonoid locality at Khao Nong Hoi (KNH) (Fig. 4), in ascending order:

KNH1: Parafusulina quasigruperaensis Sheng, 1963; Thailandina hongnusonthinae Toriyama and Kaninera, 1968; Schubertella mullerriedi Thompson and Miller, 1944; and Misellina confraspira Leven, 1967.

KNH2: This bed basically yields only the Perrinites ammonoid fauna.

KNH3: Parafusulina gruperaensis brevica Sheng, 1963; Rugosochusenella tenuis (Toriyama, 1975); Misellina confraspira; Misellina claudiae (Deprat, 1912); Thailandina hongnusonthinae; Schubertella mullerriedi; and Armenia karinae (Kochansky-Devide and Ramovs, 1955).

KNH4: Parafusulina akasakensis (Deprat, 1914); Parafusulina gruperaensis brevica; Pseudofusulina sp.; Thailandina sp.; Parafusulinal subtilis Leven, 1992; Pseudorelchellnla sp.; Misellina claudlae; and Misellina sp.

The following fusulinids were collected with Perrinites from the uppermost Khao Khad Formation in the quarry (SBQ), 4.25 km south to the Khao Plong Phrab section, Amphoe Phra Phutthabat: Schubertella sp., Schwagerina sp., Parafusulinal subtilis, Pseudoendothyra sp., Misellina confraspira, Misellina cf. claudiae, Nankinella sp., Rugosochusenella tenuis, Thailandina hongnusonthinae, and Parafusulina quasigruperaensis.

Based on general constituents of the fusulinids, it is suggested that the Perrinites-bearing beds probably be correlate with the lower part of the B Formation, most likely the B^sub 2^-B^sub 3^, or even including the bottom B^sub 4^, in the Khao Plong Phrab section (Toriyama et al., 1974).

It is well known that this fusulinid fauna is certainly younger than the Artinskian forms from the Urals, and probably of Bolorian or even partially including the earliest Kubergandian age in Middle Asia, at least containing the sum of the Kochusu Formation, Shindy Formation and the bed of Misellina claudiae in the southeast Pamirs, all of which had been referred to the Kungurian Stage (Jin et al., 1997).

Bogoslovskaya and Leonova ( 1994) concluded that the Kubergandian above the Kungurian was equivalent to Roadian, the lower part of Guadalupian Series, characterized by the first appearance of genera Paraceltiles Gemmellaro, 1887; Siacheoceras Gemmellaro, 1887; Epiglyphioceras Spath, 1930; and Tauroceras Toumanskaya, 1938a. So far as known, all these genera are absent from the Perrinites Zone of southcentral Thailand. It seems that the fossil-bearing strata there are of Kungurian age, although the associated fnsulinid fauna has already had some Kubergandian (Roadian) constituents and Perrinites gouldi seems to have somewhat higher occurrence in Texas.

DISTRIBUTION OF PERRINITID AROUND THE WORLD

Perrinitids are usually thought to be provincial ammonoids. They are known to occur in abundance at only a few localities around the world and are entirely absent from some classic, highly diverse Permian ammonoid localities, such as the Urals in Russia and Kazakhstan. Nevertheless, they have figured prominently in the Lower to lower Middle Permian ammonoid zonation, namely the Zones of Properrinifes, Metaperriniles, and Perrinites. The perrinitids presumably originated from the Shumarditidae during the Asselian, and underwent rapid extinction in the Roadian without descendants. Therefore the occurrence of perrinitids around the world has attracted much attention of paleontologists (Leonova, 1983, 1996; Tharalson, 1984).