Abdel Galil A. Hewaidy

Macrofauna and paleobiogeography of the Callovian Tuwaiq Mountain Formation in central Saudi Arabia

Forty-six Callovian macrofaunal species including 13 brachiopods, 19 bivalves, and 14 gastropods were collected from three surface sections—Shaib Al Hisyan, Khashm Al Giddiyah, and Dirab—in the Tuwaiq Mountain Formation around Riyadh City in central Saudi Arabia. The fauna is discussed systematically and with respect to biostratigraphic implications and its paleobiogeographic distribution. Four macrobiozones with two barren intervals are identified. These zones are from base upward: Pholadomya (Bucardiomya) lirata, Barren interval (1), Sphringanaria capax, Pholadomya inornata, and Coral Zone of Middle Callovian age and Barren interval (2) of Middle to Late Callovian age. The paleobiogeographic distribution of the fauna confirmed the endemism along the southern Tethyan margin of the Ethiopian Province.

Microfacies and depositional environments of Jurassic (Callovian) Tuwaiq Mountain Formation in central Saudi Arabia

Three stratigraphic sections of the Callovian Tuwaiq Mountain Formation at Shaib El-Hisyan, Khashm Al-Giddayah and Dirab, near Riyadh City, central Saudi Arabia have been studied to distinguish their microfacies features and the equivalent probable depositional environments. Lithostratigraphically, the Tuwaiq Mountain Formation is subdivided into two lower and upper Tuwaiq members. The part that informally is known as upper Tuwaiq Member is subdivided from base to top into T1, T2, and T3 members, respectively. The microfacies analysis of the Tuwaiq Mountain Formation led to the recognition of 12 microfacies types (FT1–FT12) that are grouped into three associations: (1) open platform facies association (FT1–FT5); (2) high-energy shoals of ooids and patch reefs facies association (FT6–FT9); and (3) restricted carbonate platform facies association (FT10, FT12). The lower part of the Tuwaiq Mountain Formation is characterized by relative abundance of wackestone and wacke/packstone facies that are capped by thin peloidal molluscan floatstone facies. The former indicates a quiet open platform environment with periodic agitation, while the later indicates deposition in a sand shoal environment. The facies of basal unit of the upper Tuwaiq Mountain Formation, T1, are enriched with dense micrite matrix and shell fragments of epifaunal and deep infaunal organisms (e.g., Pholadomya spp.). The microfacies pattern of Baladiyah Member (T1) indicates a quiet open platform with low and sometimes high water circulation. The Maysiah Member (T2) is composed of hard limestone with abundance of coralline microfacies in framestone, grainstone, and packstone textures suggesting a high-energy shallow reefal environment with periods of quiet open platform conditions. This shallow reefal environment becomes more restricted southward, where shales and algal dolomitic grainstones were formed. The Daddiyah Member (T3) that made up of chalky limestone with chert intercalations is predominated by matrix-support lime mudstone, wackestone, and packstone facies. These microfacies reflect open platform with slightly low circulation below fair-weather wave base with period of restricted marine conditions forming rudstone microfacies. Southward, these environments became shallower and subjected to considerable quartz influx in an agitated sand shoal.

A new anthracothere (Artiodactyla) from the early Oligocene, Fayum, Egypt, and the mystery of African ‘Rhagatherium’ solved

Abstract. Recent work on new anthracothere (Mammalia, Artiodactyla) specimens from the Jebel Qatrani Formation, early Oligocene, Fayum, Egypt, has revealed the presence of a new genus. Nabotherium new genus is described on the basis of a partial skull, several mandibular and maxillary specimens, and isolated teeth. The new genus exhibits a distinctive combination of features not seen in other Paleogene anthracotheres. The most noticeable characteristics of the new genus include the presence of large and well-developed upper and lower canines, caniniform third incisors, the presence of only a short diastema between the canine and first premolar, and broad, bunodont cheek teeth. This is in contrast to other contemporary anthracotheres, including other forms from the Fayum, which show a spatulate third incisor, a reduced canine, a much longer canine-premolar diastema, and more narrow, bunoselenodont cheek teeth. The presence of a relatively short rostrum with closely packed incisors, low-crowned and simple premolars, and low-crowned, bunodont molars indicates that members of the new genus would have been more efficient at crushing foods than slicing vegetation, and suggests a more varied herbivorous and frugivorous diet than was favored by other, more bunoselenodont Fayum anthracotheres.