# MIDIAN CORALS OF EAST THAILAND: A SIGNIFICANT FAUNA. COMPARISON WITH SIMILAR FAUNAS OF SOUTHEAST ASIA

Henri Fontaine, Sirot Salyapongse, Daniel Vachard

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Henri Fontaine, Sirot Salyapongse, Daniel Vachard. MIDIAN CORALS OF EAST THAILAND: A SIGNIFICANT FAUNA. COMPARISON WITH SIMILAR FAUNAS OF SOUTHEAST ASIA. 2002. [hal-04343212](https://hal.science/hal-04343212v1).

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Distributed under a Creative Commons CC0 1.0 - Universal - International License
MIDIAN CORALS OF EAST THAILAND: A SIGNIFICANT FAUNA. COMPARISON
WITH SIMILAR FAUNAS OF SOUTHEAST ASIA

by

Henri FONTAINE*, Sirot SALYAPONGSE** and Daniel VACHARD***

* Missions Etrangères de Paris, France (former senior expert of CCOP based in Bangkok, Thailand)

**Geological Survey, Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand

***Paléontologie, Sciences de la Terre, Université de Lille, 59655 Villeneuve d'Ascq cedex, France

**Abstract:** New discoveries of Permian corals in east Thailand confirm that Midian corals are peculiar, and accordingly, good stratigraphical markers. The Genera *Aridophyllum* and *Parawentzelella* which have been considered synonyms of the Murgabian Genus *Ipciphyllum* by a few authors, differ actually from this genus in the characteristics of their skeleton and because of a temporal heterogeneity. The limestones of the eastern part of east Thailand are mainly Midian in age, and locally Wuchiapingian in age. The Midian corals are commonly in abundance; they were able to build reefs. In the Wuchiapingian, corals are on the decline.

**Keywords:** Midian corals, *Aridophyllum saithongense* n. sp., East Thailand, Cambodian border.

**Special note by Thi Than Hoang (December 2023):**

This manuscript is one of nearly 40 notes left behind by Henri Fontaine* when he has passed away on 31 January 2020. Prepared in 2002 with the participation of Sirot Salyapongse and Daniel Vachard; it contained two plates, in one of them there was *Aridophyllum saithongense* n. sp. Unfortunately, they have not been found. Fortunately, almost thin sections mentioned in this paper have been grouped and kept at the Museum Sirindhorn in Thailand (province Kalasin); those which are stored at the Museum or missing are indicated in parentheses of each locality in this paper (ex: ref. Thin Section Collections Henri Fontaine, box T+number).

Hoang T.T. has found this manuscript, among his documents, in two forms: a paper copy with hand corrections and a digital copy saved on 13-06-2020 with more details. The digital copy is this one. Hoang T.T. modified the presentation of the text by adding: key words, chapter numbers, columns 5, 6, 11 to 16 of the table following the text, thin sections of each locality missing or stored at the Museum Sirindhorn, and full name of journals in references.

To protect the discovery of the principal author (Henri Fontaine) while leaving open access for researchers, this manuscript will be deposited on https://hal.science.

* Thi Than Hoang (2019) – Scientific life of a French catholic missionary: Henri Fontaine (1924- ?) _ La vie scientifique d'un missionnaire catholique français: Henri Fontaine (1924- ?). Annales de Paléontologie 105 (2019), 173-190.

# 1- INTRODUCTION

Permian limestones are widespread in the eastern part of east Thailand along the Cambodian border. They are the continuation of limestones relatively well known in western Cambodia from Sisophon to Pailin and Treng. These Cambodian limestones are Late Murgabian-Midian (corresponding to the Capitanian in the newly
proposed international division of the Permian) in age. They are overlain by poorly
fossiliferous beds. Several papers have concerned these limestones of Cambodia;
the most recent papers have been written by Ishii et al. 1969, Nguyen D. T. 1979 and
1986. The relationship between east Thailand and west Cambodia has already been
suggested by the discovery of one species (Lepidolina multiseptata ) in east Thailand
(Pitakpaivan and Ingavat 1980). The Genus Lepidolina , a fusulinid genus, had been
erected by Lee (1933) on the basis of Neoschwagerina multiseptata (Deprat) found
near Sisophon in west Cambodia. The Yabeina - Lepidolina zone is the equivalent of
the Midian. The relationship between east Thailand and west Cambodia suggested
by one species in the past is presently based on diverse faunas (Fontaine et al.
1997).

The limestones of east Thailand and west Cambodia were deposited on a shelf in relatively stable condition. They present different facies, from crinoidal limestone poor in fossils other than crinoids to limestone especially rich in diverse faunas and floras (algae). They were deposited in shallow and well aerated waters. Locally, micritic limestone indicates deeper and more quiet environment, seemingly lagoonal. All these limestones are only gently folded. They are a monotonous formation exposed widely in east Thailand between the Cambodian border and the road from Sa Kaeo to Chanthaburi. They are in sharp contrast with the Permian outcrops known near the road from Sa Kaeo to Chanthaburi and west of this road; there, limestones belong to a wider spectrum of Permian ages (Sugiyama and Toriyama 1981, Fontaine et al. 1996 and 1997) and are associated with cherts which have yielded Capitanian to Dzhulfian radiolarians (Sashida et al. 1993 and 1997). Further west, limestone becomes very rare in the Permian sediments and is older than the Midian.

During the last two years, thirteen Permian localities of east Thailand have
yielded corals which commonly form rich and diverse assemblages, consisting of
Tabulata, solitary, fasciculate and massive Rugosa. Nine genera and ten species
have been identified.

At many localities (Khao Phai, Khao Tham, Khao Makka, Khao Daeng, Khao Ta Ngok, Khao Bang Phreek, hill north-northwest of Khao Sa Ko Krabu, Khao Laem and the northern foot of Khao Phlap Phlung Thong), the corals are associated with large evolved Neoschwagerinidae (Yabeina, Lepidolina) as well as with other fusulinids (Kahlerina, Reichelina, Codonofusiella and others) indicating a high horizon of the Permian and more precisely a Midian age.

At a hill of Ban Sai Thong area, a massive coral has been found and is not associated with fusulinids, it might belong to an even higher horizon corresponding to the boundary between Midian and Dzhulfian (= Wuchiapingian) or the lowermost Dzhulfian. Another hill (Khao Kaew) has yielded faunas restricted to solitary Rugosa without disseпiments, associated with Colaniella and Chenella indicating a Dzhulfian age. Khao Ikia has yielded also Colaniella.

In brief, the Permian of east Thailand near the Cambodian border is characterized by widespread Midian limestones which extend into western Cambodia. Above these limestones, the Dzhulfian is represented very locally by limestones poor in foraminifers and especially corals, but rich in calcareous sponges. Dzhulfian limestone is unknown so far in western Cambodia. The Dorashamian (= Changshingian) has not been clearly documented in east Thailand; it appears to be absent. It corresponds to a marine regression as indicated by the limestone pebbles covering Khao Ikia. In Cambodia, a tendency to regression is already marked by the temporary presence of bauxite and fossil wood at the base of the Midian. During the Dzhulfian, the regression seems to be complete in Cambodia.

2- CORAL LOCALITIES

The coral localities are small to large limestone hills, reaching elevations of 200 to 700 meters above sea level. Limestone is commonly thickly bedded to massive, displaying various shades of gray. These localities are mentioned in the following lines, from the north to the south, with their corals and the most important associated fossils. Eight localities (Khao Chakan, Khao Makka, Khao Daeng, Khao Ta Ngok, Khao Bang Phreek, hill north - northwest of Khao Sa Ko Krabu, Khao Laem and Khao Kaew) had already been described (Pitakpaivan and Ingavat 1980, Sugiyama and Toriyama 1981, Fontaine et al. 1996 and 1997); however, some new data are provided in this paper. Five new localities are added in this paper (Khao Phai, Khao Tham, Khao Phlap Phlung Thong, Ban Sai Thong, Khao Ikia); moreover,
two other localities (Khao Phan and Khao Phu Hip) are mentioned because they belong also to the same age and the same area although they have not yielded corals so far.

**Locality 1 or Khao Phai** (13°40'20"N, 101°57'55"E; samples T5346 to T5354) is a small hill very rich in diverse fossils. Corals consist of rare solitary Rugosa without dissepiments (not identified) and numerous compound Rugosa (*Waagenophyllum, Parawentzelella, Multimurinus*). Algae are prolific and diverse, locally with abundant *Pseudovermiporella nipponica* Endo. Foraminifers are in abundance (see table); they consist mainly of "Glomospira" sp., *Lepidolina multiseptata* (Deprat) and *Hemigordius* sp. Other foraminifers are: *Baisalina pulchra* Reichel, *Robuloides lens* Reichel, *Kahlerina* sp., *Neoendothyra, Pachyphloia, Climacammina*. Gastropods are up to 5 cm long. Bryozoans and bivalves are rare. Calcispheres are common. This fauna indicates a Late Midian age. The limestone is a packstone. (All these thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T28).

**Locality 2 or Khao Phan** (13°40'N, 101°56'20"E; samples T5335 to T5340): The limestone is commonly a wackestone. It is rich in bryozoans. It does not contain corals. It has yielded some foraminifers (*Reichelina, Codonofusiella, Neohemigordius* and a few smaller foraminifers); see table. Calcispheres are well represented. *Pseudovermiporella nipponica* is very locally in abundance. Calcareous sponges are very rare. This fauna indicates a Dzhulfian age. (All these thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T27).

**Locality 3 or Khao Chakan** (13°39'40"N, 102°05'50"E; samples T5043-T5044, T5523 to T5526). In the past (Sugiyama and Toriyama 1981), fusulinids (*Parafusulina* and *Yangchienia*) were found in a crinoidal limestone of the western part of Khao Chakan in association with a solitary coral (*Khmerophyllum* cf. *cambodgense* Fontaine); they were considered indicating a late Early to Middle Permian age, an age appearing older than that of the other limestones of the area. Hada et al. 1997 mentioned cursorily *Lepidolina* at Khao Chakan. In October 1997, abundant fusulinids have been found by the authors of this paper at the eastern part of Khao Chakan where crinoids are less common than at the western part of the hill. They consist of "*Parafusulina*", *Yangchienia* and *Schubertella*, indicating a vague age from Kubergandian to Midian. However, they are associated in a few thin sections with *Robuloides* aff. *acutus* Reichel 1945 and "*Angelina*" cf. *arpaensis* Pronina 1990; these two species indicate a Midian age. "*Angelina*" Altiner 1986 was known only in Turkey and in Transcaucasia up to now; it is mentioned in eastern Asia for the first time. The name "*Angelina*" is invalid at present and must be replaced by another name in the future. Bryozoans are locally in abundance. Calcispheres are common and consist of *Diplosphaerina inaequalis* (Derville 1931) and *Mendipsia conili* (Nguyen 1980). (Thin section T5043 is missing, T5044 and others are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T26 and T29).

**Locality 4 or Khao Tham** (13°39'30"N, 101°55'10"E; samples T5325 to T5330): The limestone of a group of three small hills is not very fossiliferous; it is commonly a wackestone, rarely a packstone. *Tubiphytes* and *Bacinella* are common fossils. *Diplosphaerina inaequalis* is present. Fusulinids and smaller foraminifers are rare. They consist of the following taxa: *Pseudoreichelina slovenica* (Kochanski-Devide 1966), *Dunbarula, Baisalina* and others; see table. *P. slovenica* is usually in older beds. Fasciculate corals (*Waagenophyllum*) occur occasionally. That limestone belongs to the Midian. (All these thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T27).

**Locality 5 or Khao Makka** (13°38'N, 102°06'30"E; samples T5045 to T5052) has already been the subject of two papers (Pitakpaivan and Ingavat 1980; Fontaine et al. 1997). It is rich in corals (*Sinopora, Waagenophyllum, Multimurinus*) and other fossils. Foraminifers are in abundance (*Lepidolina, Codonofusiella, Reichelina*, *Kahlerina* and other fusulinids). Algae are common. That limestone is Midian in age. (Thin section T5049 is missing, others are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T26).

**Locality 6 or Khao Daeng** (13°28'30"N, 102°17'E; samples T5019 to T5025): Limestone is overlain by a conglomerate. It is partly dolomitised. It is locally rich in
fossils and contains Tabulata (Sinopora) and rare fasciculate Rugosa (Waagenophyllum) which have already been described (Fontaine et al. 1997). They are associated with Reichelina, Codonofusiella, Pseudodunbarula; algae consist of Dasycladaceae and Solenoporaceae (Fontaine et. al. 1996, 1997). That limestone is, at least, partly Dzhulfian in age. (Thin sections T5019, T5020, T5025 are missing, others are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T15 and T26).

**Locality 7 or Khao Tham Ikia** (13°27'25"N, 102°07'20"E; samples T5513 to T5522): That hill is built up by a massive limestone associated with a conglomerate composed exclusively of limestone pebbles. These rocks represent a limestone associated with the products of its erosion. The limestone is rich in calcareous sponges and bryozoans. It contains algae, some smaller foraminifers, a few bivalves, a few gastropods and very rare ostracods. The foraminifers include a small and relatively primitive species of Colaniella, C. minima Wang 1956, a species common in the Dzhulfian (Jenny-Deshusses and Baud 1989). Algae are represented by Dasycladaceae and locally abundant Solenoporaceae. See the table. The limestone is locally dolomotized. It is Dzhulfian in age. Genus Colaniella Likharev is a good age indicator; it appeared in the Midian, became common during the Dzhulfian, declined during the Dorashamian and disappeared at the end of the Permian. (All these thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T29).

**Locality 8 at the northern foot of Khao Phlap Phlung Thong** (13°27'N, 102°12'20"E; samples T5374 to T5377). The limestone is a packstone. Fossils are diverse. Corals consist of fasciculate Rugosa represented by Waagenophyllum. They are associated with abundant algae (Dasycladaceae and common Solenoporaceae) and with foraminifers (Neoschwagerina, Yabeina, Codonofusiella and others). Brachiopods are locally in abundance. Bryozoans, sponges, gastropods and crinoids are also present. This fauna indicates a Murgabian – Early Midian age. See table where the fossils of two samples are listed. (All these thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T28).

**Locality 9 or three limestone hills of Ban Sai Thong area.** A hill, 269 m high (Locality 9a: 13°25'50"N, 102°14'10"E; samples T5378 to T5382), is very rich in bryozoans and calcareous sponges. Gastropods are rare. Lepidolina would have been found at the northern foot of that hill in the past (Information from S. Salyapongse). Another hill, 1 km south of the first one (Locality 9b: 13°25'05"N, 102°14'10"E; samples T5383 to T5389) is rich in diverse bryozoans. Brachiopods occur occasionally. Other fossils are relatively rare. Fusulinids have not been noticed so far. A single massive coral (Aridophyllum) has been collected. The third hill is located 1.5 km southeast of the second one (Locality 9c: 13°24'N, 102°14'45"E; samples T5390 and T5391). It contains bryozoans, brachiopods, calcareous sponges. Very poorly preserved fusulinids have been noticed. See table. The limestone of these hills extends apparently from Midian to Dzhulfian. (All these thin sections T5378 to T5391 are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T28).

**Locality 10 or Khao Phu Hip** (13°23'N, 102°15'10"E; samples T5392 and T5393): Limestone is massive. It is locally a packstone rich in fusulinids: Lepidolina multiseptata (Deprat) and Colania cf. douvillei (Ozawa). In other places, it is wackestone to packstone containing sponges and bryozoans in abundance. See table. It is Midian in age. (These thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T28).

**Locality 11 or Khao Ta Ngok** (13°20'N, 102°19'30"E; samples T5037 to T5041): This limestone hill is elongated and its northern part is called Khao Kok Mamuang. At first, it had been visited at two places of its western side. Fusulinaceans were found and consisted of Lepidolina multiseptata, Kahlerina and Codonofusiella. They were associated with algae (Mizzia, Permocalculus, Koivaella) and smaller foraminifera (Pachyphloia, Climacammina, Globivalvulina, Tetrataxis). Corals appeared to be very rare; only a single sample of Tabulata (Sinopora) was noticed (Fontaine et al. 1997).

Recently, two new localities have been visited. At the south-western side of Khao Ta Ngok (13°18'06"N, 102°20'40"E; samples T6616 to T6621), limestone is rich in fusulinaceans and contains rare massive corals (T6621) and some bryozoans. The foot of the southern end of Khao Ta Ngok (13°17'48"N, 102°20'54"E; samples T6622 to T6627) is built up by shale, sandstone, volcanic rock and minor limestone
(containing foraminifera, calcareous sponges and bryozoans). Limestone is
prominent only at the top of the hill. (Thin sections T5038, T5039, T5041 are kept at
the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, in Box T26, T5040
in Box T15, all others are missing).

Locality 12 or Khao Bang Phreek (13°15'30"N, 102°18'E, sample T4974?) is built up by a dark massive limestone which is rich in crinoids and bryozoans. Sponges are locally in abundance and in life position. Stromatolites occur occasionally. Solitary Rugosa (Tachylasma, Lophocarinophyllum) are rare and are associated with foraminifers (Codonofusiella, Reichelina, Kahlerina, Pseudodunbarula, Rauserella and maybe Lepidolina) and algae consisting of Dasycladaceae (Fontaine et al. 1997). That limestone is Midian and/or Dzhulfian in age. (Thin section T4974 is kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T15).

Locality 13 or Khao Kaew (13°06'N, 102°24'20"E; samples T4972 and T4973), limestone contains bryozoans and rare solitary Rugosa (Paracaninia), associated with Colaniella and Chenella (Fontaine et al. 1997), indicating a Dzhulfian age. (These thin sections is kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, T4972 in Box T26, T4973 in Box T15).

Locality 14 at a hill north-northwest of Khao Sa Ko Krabu (13°03'30"N, 102°25'30"E; sample T4961), limestone is rich in crinoids. At the eastern foot of the hill, it contains compound Rugosa (*Waagenophyllum*, *Multimurinus*) which are associated with *Lepidolina*, a few smaller foraminifers and *Tubiphytes* (Fontaine et al. 1997). It is Midian in age. (Thin section T4961 is kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T26).

Locality 15 or Khao Dun Ta (13°02'50"N, 102°27'E; samples T4970 and T4971): Limestone is poor in fossils with the exception of calcareous sponges and crinoids (Fontaine et al. 1997). It is thought to be Dzhulfian in age. (These thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box 26).

Locality 16 or Khao Laem (13°01'20"N, 102°27'E; samples T4963 to T4969): *Waagenophyllum* is associated with a rich assemblage of foraminifers (*Lepidolina*, *Kahlerina*, *Hemigordiopsis renzi* Reichel) and algae consisting of Dasycladaceae and Solenoporaceae (Fontaine et al. 1997). (All these thin sections are kept at the Museum Sirindhorn, Thin Sections Collections Henri Fontaine, Box T26, except T4969 missing).

TABLE: Faunas of the localities recorded in this paper
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3-

<table><caption>Table - Fauna of the localities recorded in this paper (continued)</caption><thead><tr><th>Localities</th><th>1</th><th>2</th><th>3</th><th>4</th><th>5</th><th>6</th><th>7</th><th>8a</th><th>8b</th><th>9a</th><th>9b</th><th>9c</th><th>10</th><th>11</th><th>12</th><th>13</th><th>14</th><th>15</th><th>16</th></tr></thead><tbody><tr><td><strong>Fusulinidae (continued)</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Afghanella</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>« Parafusulina »</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Rausenella</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Dunbarula cf. kitakamiensis</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Dunbarula schubertellaeformis</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Schubertella</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Inojapanella elongata</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Corals (Tabulata)</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sinopora</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Corals (Rugosa)</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Khmerophyllum</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Waagenophyllum kueichowense</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Waagenophyllum pulchrum</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Aridophyllum</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Parawentzelella gubleri</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Multimurinus</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Tachylasma</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Lophocarinophyllum</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Paracaninia</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><strong>Bryozoans</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

## THE CORALS

Tabulata are rare and represented only by Genus *Sinopora* and only the species *Sinopora asiatica* (Mansuy). They have been found only at two localities: Khao Makka and Khao Ta Ngok. S. asiatica is a species which has been introduced by Mansuy (1913, p. 111-112, pl. 11, fig. 13) and is based on samples collected near Sisophon in west Cambodia. Other localities of west Cambodia have yielded the same species: Phnom Kraupeu, Phnom Ndag and Phnom Banteay Neang (Fontaine 1955, p. 76, pl. 4, figs. 4-5; pl. 5, fig. 8). S. asiatica has a long stratigraphical range and exists also in the Murgabian (Neoschwagerina zone).

Solitary Rugosa are not in abundance; they are scattered in the limestone of a few localities: Khao Chakan, Khao Kaew, Khao Bang Phreek and Khao Phai. They belong to five genera: *Lophophyllidium*, *Khmerophyllum*, *Lophocarinophyllum*, *Tachylasma* and *Paracaninia*.

Compound Rugosa are rare to common at Khao Daeng, Khao Phlap Phlung Thong, Khao Tham, Khao Ikia and two small hills near Khao Tham; they are only fasciculate. They are prolific and diverse at other localities: Khao Makka, hill north-northwest of Khao Sa Ko Krabu, Khao Laem and Khao Phai; they are fasciculate and massive. The compound corals are very important for stratigraphy; they are described in the following and two genera (*Aridophyllum* and *Parawentzelella*) are mentioned in Thailand for the first time.

### Genus *Waagenophyllum* Hayasaka 1924

The Genus *Waagenophyllum* is common in east Thailand and has been found at seven localities. It has already been described at Khao Makka as *Waagenophyllum kueichowense* Huang 1932 and at three other localities (Khao Daeng, a hill north-northwest of Khao Sa Ko Krabu, Khao Laem) as *Waagenophyllum pulchrum* Hamada 1962 (Fontaine et al. 1997). These two species are easy to recognize, even in the field with the naked eye. Their corallites differ in size with diameters of 8 mm for *W. pulchrum* and of about 5 mm for *W. kueichowense*. This paper (Pl. 2, fig. 3) provides again a photograph of a transverse section of *W. kueichowense*, sample T 5051 from Khao Makka.

The samples newly collected from Khao Tham, Khao Phai, Khao Ikia and the northern foot of Khao Phlap Phlung Thong belong to the same two species. *Waagenophyllum pulchrum* has been found at Khao Tham. *Waagenophyllum kueichowense* is in abundance at Khao Phai where the corals are commonly 40 cm in diameter. This species exists also at the northern foot of Khao Phlap Phlung Thong
and probably at Khao Ikia. The single sample collected from Khao Ikia displays thick septa which unite at the corallite periphery; dissepiments are no more visible. The diameter of the corallites and the number of septa in this sample are the same as for *Waagenophyllum kueichowense*.

## Genus *Aridophyllum* Zhao 1976

Genus *Aridophyllum* has been introduced by Zhao in 1976 for massive corals collected from the lower part of the "Wuchiaping Formation". Corallite walls which are relatively thick and the large development of clinotabulae distinguish this genus from Genus *Ipciphyllum*. *Aridophyllum* appears to be descended from Genus *Waagenophyllum* and might be considered a cerioid *Waagenophyllum*. The sample described in the following belongs to a *Aridophyllum* species of which corallites are not perfectly welded. Accordingly, we cannot follow the point of view of Lin et al. (1995, p. 586-587) who regard *Aridophyllum* as a synonym of *Ipciphyllum*. Ezaki (1994, p. 168-169) seems also to consider *Aridophyllum* synonymous with *Ipciphyllum* and indicates a stratigraphic range for this last genus extending up to the end of the Permian in South China.

*Aridophyllum* is mentioned for the first time in Thailand and even in Southeast Asia.

*Aridophyllum saithongense* n. sp.

Pl. 1, figs. 1 - 4

**Material:** Sample T5383 from Ban Sai Thong area, deposited at the Department of Mineral Resources, Bangkok; geographic coordinates: 13°25'05"N, 102°14'10"E.

**Description:** Cerioid coral. Corallites with thick walls. Septa thickened at corallite periphery.

In transverse sections, corallites are 6 to 8 mm in diameter. They are polygonal in section, showing a tendency to dissociate at a corner from the adjacent corallites, thus leaving empty a very small and commonly triangular space between the corallites. Corallite walls are relatively thick. Septa are of two orders, 22+22 to 24+24 in number. They are thick at their point of attachment to the corallite wall. Adaxially, they may be thin and slightly zigzaged over a short distance, and then in the tabularium, they are slightly thickened. Major septa almost reach to the columella. Minor septa are 3/4 as long as the major septa. Columella is relatively well developed, with a diameter of 1.5 to 2 mm. It is made of a median plate, septal lamellae and axial tabellae.

In longitudinal sections, dissepiments are small, slightly irregular in size, arranged in 3 to 6 rows. The tabularium is 1.5 mm wide: it consists mainly of clinotabulae. Horizontal tabulae are very narrow and 0.2 to 0.5 mm wide. They disappear locally. They are about 30 in a vertical distance of 1 cm. Columella is tightly constructed, made of arched tabellae which are about 40 in a vertical distance of 1 cm.

**Affinities:** The coral described above displays strong affinities with *Aridophyllum anshunense* Zhao (1976, p. 220, pl. 1, figs. 15a-b) in the shape and the size of the corallites, the number and the length of the septa, the size of the columella and the development of the dissepiments. However, the empty spaces between the corallites appear as a peculiar characteristic allowing to recognize a new species. They are not in abundance, but they are almost regularly distributed.

**Age:** The stratigraphical occurence of the coral of east Thailand appears to be Midian near the boundary between Midian and Dzhulfian or maybe in the lowermost part of the Dzhulfian.
## Genus *Parawentzelella* Fontaine 1961

The Genus *Parawentzelella* is very close to *Ipciphyllum* Hudson 1958, but differs from this last genus by the presence of canals, placing tabularia of adjoining corallites into contact. At first look, these canals may suggest a parasitic activity. However, they show a very regular shape, respecting the structure of the coral. In addition to that, there is a temporal heterogeneity between *Parawentzelella* and *Ipciphyllum*. The first genus belongs to the *Yabeina* - *Lepidolina* zone while the second genus belongs to the *Neoschwagerina* zone. Accordingly, the Genus *Parawentzelella* cannot be considered a synonym of *Ipciphyllum* as it was suggested by Lin et al. (1995, p. 586-587).

### *Parawentzelella gubleri* Fontaine 1961

1961 - *Parawentzelella gubleri* Fontaine, p. 191-192, pl. 28, fig. 4; pl. 31, fig. 9; pl. 34, fig. 7.

**Material:** Sample T5350 from Khao Phai; geographic coordinates: 13°40'20"N, 101°57'55"E.

**Description:** Cerioid coral, 40 cm in diameter, displaying relatively small corallites.

In transverse sections, corallites are 3 to 4 mm in diameter. Septa are of two orders, 12+12 to 14+14 in number. Minor septa are slightly shorter than major septa. Columella is well developed, it is 0.8 to 1 mm in diameter. It commonly displays a median plate. Corallite walls are pierced by canals which are located exclusively at corallite corners and display an angular shape in following interseptal spaces of two adjacent corallites. Lonsdaleoid dissepiments occur occasionally; they are very rare.

In longitudinal sections, dissepiments are arranged in 2 to 4 rows. Tabularium is 0.5 to 0.6 mm wide. Clinotabulae are present, but horizontal tabulae are well developed and are 40 in number in a vertical distance of 1 cm. Columella is tightly constructed.

**Affinities:** The sample collected from Khao Phai is very similar to the sample found in west Cambodia and described as *Parawentzelella gubleri* n. sp. (Fontaine 1961). It differs from this last sample only by a slightly greater length of the minor septa.

**Age:** Midian.

## Genus *Multimurinus* Fontaine 1967

The Genus *Multimurinus* has been found at three localities of east Thailand. Two localities (Khao Makka and a hill north-northwest of Khao Sa Ko Krabu) have already been recorded in a previous paper (Fontaine et al. 1997). The third locality is reported in this paper.

### *Multimurinus* cf. *makkaensis* Fontaine 1997

Pl. 2, figs. 1 - 2

1997 - *Multimurinus makkaensis* Fontaine et al., p. 122, pl. 2, figs. 1 – 2; pl. 3, figs. 1 - 3

**Material:** Sample T5353 from Khao Phai where other corals belonging to *Waagenophyllum* and *Parawentzelella* have been found.

**Description:** Massive coral, about 30 cm in diameter. Corallite walls are very discontinuous and typical of Genus *Multimurinus*; they reach a thickness of 0.5 mm.

In transverse section, corallites are 7 to 10 mm in diameter. Septa are of three orders. They are thick in the axial part of the corallite while they are thin and more or less zigzaged at corallite periphery. Major septa almost reach to the columella, they
are 14 to 16 in number. Septa of the second order are slightly shorter than major septa. Septa of the third order are a little shorter than septa of the second order. Columella is relatively small, 0.7 to 1 mm in diameter. Lonsdaleoid disseпpiments exist, they are rare.

In longitudinal section, disseпpiments are small, slightly irregular in size. They are arranged in 5 to 8 rows. Tabularium is 0.5 to 0.8 mm wide. It consists of clinotabulae and horizontal tabulae. The latter are 0.3 to 0.4 mm wide.

**Affinities:** This sample displays strong affinities with *Multimurinus makkaensis*, but its corallites are smaller in size as well as the other accompanying characteristics.

**4- CONCLUSION:** The stratigraphic significance of the compound corals

The compound corals described above form an assemblage characteristic of the Midian. When they are noticed in the field, it is easy to find large evolved Neoschwagerinidae (*Yabeina* and *Lepidolina*) associated with them. They clearly differ from the Murgabian corals and they are the last important assemblage of compound Rugosa before the disappearance of massive Rugosa at the beginning of the Dzhulfian.

In central Thailand where Murgabian limestones are widespread, the Murgabian corals are dominated by the genera *Ipciphyllum* (massive coral) and *Pseudohuangia* (fasciculate coral) which, with other less important genera such as *Chaophyllum* (fasciculate coral) and *Crassiparietiphyllum* (massive coral), disappear completely at the end of the Murgabian. See Fontaine et al. 1994. In the Midian, *Ipciphyllum* is replaced by two other massive corals: *Aridophyllum* and *Parawentzelella*. *Waagenophyllum* is very rare in the Murgabian of central Thailand; it is in abundance in the Midian limestones of east Thailand. *Multimurinus* is represented by several species in the Murgabian of central Thailand (Fontaine et al. 1994); it is known so far by a single species in the Midian of east Thailand.

In conclusion, the Midian assemblages of compound corals display peculiar features that allow to recognize surely the Midian.

In southeast Asia, Midian corals are presently known in west Cambodia (Fontaine 1961; Fontaine 1967), in east Thailand (Fontaine et al. 1997; this paper) and in the "Central Belt" of Peninsular Malaysia (Fontaine et al. 1988). In the three countries, they are associated clearly with evolved Neoschwagerinidae (*Yabeina* and *Lepidolina*) and other fusulinids indicating a Midian age. The Midian limestones of Peninsular Malaysia are only lenses and their fauna seems to be moderately diverse. In west Cambodia and east Thailand, limestones are thick and contain richer faunas.

The Dzhulfian limestones of east Thailand contain compound corals, but these corals are restricted to Genus *Waagenophyllum*, and maybe at a single locality, also to Genus *Aridophyllum*. *Waagenophyllum*, when present, is not in abundance; *Aridophyllum* is extremely rare and should be restricted to the base of the Dzhulfian. Corals are on the decline. On the contrary, calcareous sponges flourish and are diverse. Accordingly, they appear to replace corals in the last bio-constructions of the Upper Permian of east Thailand. They are associated with bryozoans, algae and *Tubiphytes*.

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PLATE 1

Scale bar = 1 mm

Figures 1 and 4 - *Aridophyllum saithongense* n. sp. Transverse sections. Sample T 5383 from a hill in the vicinity of Ban Sai Thong ; geographic coordinates: 13°25'05" N, 102°14'10" E.

Figures 2 and 3 - *Aridophyllum saithongense* n. sp. Longitudinal sections. Sample T 5383 as in figures 1 and 4.

PLATE 2

Scale bar = 0.5 mm

Figure 1 - *Multimurinus makkaensis* Fontaine et al. 1997. Transverse section. Sample T 5046 from Khao Makka.

Figure 2 - *Multimurinus makkaensis* Fontaine et al. 1997. Longitudinal section. Sample T 5046 as in figure 1.

Figure 3 - *Waagenophyllum kueichowense* Huang 1932. Transverse section. Sample T 5051 from Khao Makka.