Herbert H. Covert ¹, Trinh Dzanh ²,
§ç §øc Quang ², Lª Quèc Thanh ², NguyÔn M¹nh Phi ²

Limestone formations are widely distributed across the world. Limestone is easily dissolve by ground waters - through geologic time, underground caverns are formed in limestone deposits. This caverns or fissures, when exposed to the surface form open sinkholes or caverns. Through the time, these fissures can fill with various items from the landscape surface. These "fissure-fillings", sometimes called breccia, include sediments, rocks, and occationally bones - that become fossilized through the time. Fissure fillings have been processed for fossils in deposits in South America, North America, Europe, Africa, and Asia. These projects have yielded fossil birds, reptiles, and mammals. These fossil mammals include important hominid and human remains in Spain and South Africa, early primates, rodents, artiodactyls and perissodactyls in France, and early primates, rodents, and lagomorphs in China.

In ViÖt Nam, Paleozoic and Mesozoic limestone formations are also widely distributed, especially in the B¾c Bé (Northern) and B¾c Trung Bé (North of Central), in which there are many famous caverns and grottos. In these limestone massifs there are many fissure-fillings that may contain fossils.

On May 2002 while surveying Triassic age limestones in Ninh B×nh Province for exposed fissure-fillings we discovered a new mammal fossil producing locality. This locality is located at 20.07.83N, 105.52.13E. Located about 10 km south of Ninh B×nh City this locality is a dark brown breccia consisting of soil, sand, gravel, and fossil vertebrates. It is located in a light brown-grey limestone of the §ång Giao Formation. We found many mammal teeth and bones and we collected number including teeth of an orangutan, macaque, rhino, pig, a large rodent, and other mammals.

Preliminary list of specimens (please note that all taxonomic attributions are provisional pending additional study):

1- Macaca (order Primates), upper left molar, L=9.05 mm, W=8.45 mm (fig. 1).

2- cf. Hominoidea (order Primates), upper right lateral incisor, L=7.95 mm, W=5.25 mm (Pl.1, fig. 2).

3- Pongo pygmaeus (order Primates), lower 2^nd molar - in breccia, L=15.9 mm x15.2 mm (Pl.1, fig. 4).

4- Pongo pygmaeus (order Primates), lower molar - in breccia, L=14.8 mm. This block also has a second mammalian molar visible.

5- Rhinoceros (order Perissodactyla), right molar, L=39.25 mm, W=28.3 mm (Pl.1, fig. 5).

6- Rhinoceros (order Perissodactyla), right molar - in breccia, L=35.6 mm.

7- Sus (order Artiodactyla), lower third molar (Pl.1, fig. 6).

8- Sus (order Artiodactyla), lower molar, W=21.25 mm (Pl.1, fig. 7).

9- Sus (order Artiodactyla),lower third molar - in breccia, L=40.75 mm. There is also a cervid upper molar (order Artiodactyla) in this breccia.

10- A block of breccia with a number of teeth and bones including the upper molar of a cervid (order Artiodactyla), L=23.0 mm, W=21.0 mm and a canine (cf. Primate), W=5.2 mm, H=9.1 mm.

11- Pongo (order Primates), upper third molar, 12.8 mm x 14.2 mm (Pl.1, fig. 3).

12- Sus (order Artiodactyla) or Ailuropoda (order Carnivora), upper molar - in breccia, L=37.7 mm.

13- Large rodent incisor (order Rodentia), W=7.8 mm, in large piece of breccia with many other tooth and bone fragments.

14- Lingual portion of cervid molar (order Artiodactyla), W=25.3 mm - in breccia.

15- Pieces of two small mammal teeth - one appears to be an upper third molar and the other is a lower premolar.

16- Pieces of eleven large mammal teeth-including one heavily worn incisor, W=6.8 mm.

17- Seven pieces of mammal bone.

18- Mammal molar in breccia.

19- Mammal tusk in breccia (suid?), L=66.35 mm.

20- Mammal tooth in breccia (possibly Rhinoceros), H=17.0 mm.

21-Mammal bone or large tusk in breccia.

22- Cervid molar (order Artiodactyla) in breccia.

Some of the most noteworthy specimens in this collection are orangutan and macaque teeth. Specimens 3 and 11 (Pl.1, fig. 3,4) are well preserved molar of Pongo pygmaeus both of which have the crenulated enamel that is common for this species. Specimen 11 is just slightly larger than an average modern adult orangutan's upper third molar (see Swindler, 1976 for comparative data) and specimen 3 is slightly larger than any of the lower molars for which Swindler provides measurements. It has previously been reported by Hooijer (1948) [2], Kahlke (1973) [3] and Szalay and Delson (1978) [6] that fossil orangutans are often larger than the modern members of this species.

Specimen 1 represents a fairly larger Old World monkey and because it lacks the high crown relief of a colobine monkey (leaf monkey) it represents a macaque. Based on its size it could represent Macaca mulatta (the rhesus macaque), Macaca arctoides (the stump-tailed macaque), or Macaca assamensis (the Assamese macaque) monkeys that still live in Northern ViÖt Nam.

Preliminary analysis of the specimens collected at Dong Giao, Ninh Binh suggest a Middle or Late Pleistocene age due to the presence of Pongo (the orangutan) (Savage and Russell, 1983; Cuong N.L., 1992) [1,4].

The success of the fieldwork during May 2002 demonstrates the great potential of breccias that have formed as fissure and cavern fills for vertebrate paleontology in ViÖt Nam. That’s why we recommend that we focus on breccias. Here we outline a research plan that should allow the discovery and

description of a significant collection of vertebrate fossils for the Geological Museum of ViÖt Nam. Because of the widespread nature of limestone deposits in ViÖt Nam it is likely that many additional fissure fills with mammalian remains are present. Research plan in future is as follows:

1/ Systematically examine active limestone mining areas for breccias. There are extensive areas of this activity near Hµ Néi and they are quite easily accessed by good roads. When vertebrate remains are observed the location should be intensively collected.

2/ Study of fossil assemblages should focus on identifying index fossils so that they may be accurately dated.

3/ Fossils should then be studied for taxonomic, phylogenetic, and adaptive information.

This research could yield fossils that would bear directly on the following topics:

Human evolution in Asia during the Pleistocene: While a good fossil record exists from Indonesia and China for fossil humans (Homo erectus) but only a few teeth have been found in Vietnamese breccias. Additional fossils from ViÖt Nam might allow for a better understanding of the relationships among the Asia fossil humans.

Monkey, ape, and loris evolution in Southeast Asia during the Paleogene and Neogene: While modern Southeast Asia is home to a diverse and distinct primate fauna very little is known about their evolutionary history in this region. One interesting question that could be answered by this proposed research "did langurs of the Trachypithecus francoisi group inhabited limestone environments in the past or is their modern day restricted distribution in such environments a direct outcome of the deforestation of non-limestone areas?".

Mammalian evolution in Southeast Asia: While modern Southeast Asia is home to a diverse and distinct mammalian fauna little is known about the evolutionary history in this region. An improved fossil record would certainly add to our understanding of this important topic.

Reseach at limestone areas for exposed fissure fillings is likely to provide interesting and important material that will aid in the reconstruction of the natural history of Southeast Asia.

1. Cuong N. L., 1992. A reconsideration of the Chronology of Hominid Fossils in Vietnam. In: T. Akazawa, K. Aoki, and T. Kimura (eds.)-The Evolution and Dispersal of Modern Humans in Asia, pp.321-335. Hokusen-Sha.

2. Hooijer D. A., 1948. Prehistoric teeth of man and the orangutan from Central Sumatra with notes on the fossil orangutan from Java and Southern China. Zool. Meded. Rijks. Mus. Nat. Hist. 29: 175-301.

3. Kahlke H. D., 1973. A review of the Pleistocene history of the Orangutan. Asian Perspectives 15: 5-14.

4. Savage D. E. and Russell D. E., 1983. Mammalian Paleofaunas of the World. Reading, MA: Addison-Wesley.

5. Swindler D. R., 1976. Dentition of Living Primates. New York Academic Press.

6. Szalay F. S. and Delson E., 1978. Evolutionary History of the Primates. New York Academic Press.