EARLY TRIASSIC (DIENERIAN) CONODONTS FROM NORTHERN

THAILAND AND THEIR BEARING ON THE EVOLUTION OF

MULTIELEMENT APPARATUSES

Norman M. SavageGeological Sciences, University of Oregon, Eugene, Oregon 97403, USA

Michael J. OrchardGeological Survey of Canada, Vancouver, BC, V6B 5J3, Canada

Apsorn SardsudDepartment of Mineral Resources, Bangkok, Thailand 10400

Petra LutatPalaeontological Research Centre, Mahasarakham University, Thailand 44150

Location of the Phrao field area in northwest Thailand

Fossil locality west of Phrao, northwest Thailand

Narong and Supatta in their garden

Narong and Supatta’s very full garden with almost no remaining exposure

Bed PR-48 at the Phrao locality

PR-48

Beds 50, 51 and 52 at the Phrao locality

PR-50PR-51

PR-52

Spec.

1a1a

1b

1c

2a

2b

2c

3a

3b

3c

4a

4b

4c

P1 elements from Bed PR-48, Phrao section, northwest Thailand.

a, lateral, b, aboral, c, oral views

5a

5b

5c

6a

6b

6c

7a

7b

7c

8a

8b

8c

P1 elements from Bed PR-48, Phrao section, northwest Thailand

a, lateral, b, aboral, c, oral views

9a

9b

9c

10a

10c

10b

11a

11b

11c

12a

12b

12c

P1 elements from Bed PR-48, Phrao section, northwest Thailand a, lateral, b, aboral, c, oral views

Neospathodus sp. A. Bed PR-50, Phrao section, northwest Thailand, possible apparatus.

Neospathodus sp. B. Bed PR-50, Phrao section, northwest Thailand, possible apparatus.

P1

P2

M

S1

S2S3

S4S0

Fused cluster from Bed PR-51, upper and lower views.

Consisting of ?S3, S4, S1, plus an S2 and a P1.

Representative P1 elements

Bed PR-51. Neospathodus concavus

Bed PR-51. Neospathodus aff. concavus

Bed PR-51 Neospathodus chaohuensis

Bed PR-51. Neospathodus ex gr. chii

aaaaaaaaaa

A B

Neospathodus dieneri A, Morphotype 1, B, Morphotype 2

A B

Bed PR-48. Hindeodus parvus A, Side view B, Oral view

DMR Field Group: Chan, Dr. Apsorn Sardsud, New, and Oan

ConclusionsPreliminary work suggests this Phrao locality comprises several horizons with important Dienerian apparatuses.

The key to understanding the evolution of multielement Lower Triassic conodonts lies in Dienerian collections.

The Neospathodus dieneri Sweet 1970 group were amongst the first species from Neogondolella ancestors in the early Induan and represent the major rootstock for many Olenekian conodonts.

The faunas include two morphotypes of N. dieneri, plus fewer specimens of N. chii, N. concavus, and ?N. chaohuensis, all recently described from Induan-Olenekian boundary beds at Chaohu, China (Zhao et al., in press).

The faunas also contain rare specimens of Neogondolella carinata and Hindeodus parvus, species that have been regarded as casualties of the end-Griesbachian extinction.

The abundant Thailand material adds to our understanding of the evolving apparatuses of the Early Triassic but at this preliminary stage in the work it is difficult to confidently differentiate the apparatuses.

Thanks are extended to:

Narong and Supatta for allowing access to their garden and permitting us to collect rock samples,

and

The Geological Survey Division of the Thailand Department of Mineral Resources, Bangkok, and the Palaeontological Research Institute, Mahasarakham University for financial and logistic support,

and

the drivers, field assistants, and technicians.