First record of the family Dromaeosauridae (Dinosauria: Theropoda) in the Cretaceous of Gondwana (Wadi Milk Formation, northern Sudan)

I Pal ont. z. I 69 I 3J4 I 47 -489 17 Abb.,2 I Stuttgart, September 1995 I

First record of the family Dromaeosauridae (Dinosauria: Theropoda) in the Cretaceous of Gondwana

(Wadi Milk Formation, northern Sudan)

OLIVER W. M. RAUHUT ~x~ CHRISTA WERNER, Berlin*

With 7 figures and 2 tables

Kurzfassung: Die cenomane Wadi Milk Formation des Sudan lieferte eine reiche kontinentale Wirbeltierfauna. Neben Fragmenten von grofgen Theropoden verweisen disartikulierte Fuigphalangen- Elemente und ein Zahn auf die Existenz yon dromaeosauriden Theropoden in der Oberkreide des Sudan; damit ist diese Theropodenfamilie zum ersten Mal auf den Gondwana-Kontinenten nachgewiesen.

A b s tract: The Cenomanian Wadi Milk Formation in Sudan yielded a rich continental vertebrate fauna. Apart from big theropod fragments, some disarticulated elements of a pes and a tooth indicate the presence of a dromaeosaurid theropod in the Late Cretaceous of Sudan. This is the first record of this theropod family from Gondwanian continents.

Introduction The present knowledge of Cretaceous dinosaurs of Africa, in particular theropods, is ex-

tremely poor. With the exception of the just recently described Afrovenator, no articulated or partly articulated skeletons of theropods, but only isolated teeth and bones have been found (SE~NO et al. 1994).

In South Africa, strata of Late Jurassic to Early Cretaceous age have yielded some scarce theropod fragments (MATEER 1987; RICH et al. 1983). A diverse theropod assemblage described by STROMER (1915, 1931, 1934) from the Cenomanian of the Bahariya Oasis in Egypt, includes a probable ceratosaur (cf. Elaphrosaurus bambergi) and several theropod taxa of uncertain systematic position: Carcharodontosaurus saharicus, Bahariasaurus ingens, Spinosaurus aegyptiacus, Spinosaurus sp., aff. Erectopus sauvagei. Further undetermined theropod bones were also found. Unfortunately, these fossils, which were deposited in Munich, were destroyed during the Second World War.

Fragmentary remains of the genera Carcharodontosaurus, Bahariasaurus, Spinosaurus and other questionable theropods were discovered in the Cretaceous of Morocco, Algeria, Tunisia and Libya as well as Niger (WHsrtAMPEL 1990). Recently found theropod material from the Early Cretaceous of Cameroon (BRUNET et al. 1990) and Malawi (JAcoBs et al. 1990) is not yet studied in detail. If Elaphrosaurus is considered to be a ceratosaur (HoLTz 1994), no coelurosaurian theropods have been described from Africa so far (SER~NO et al. 1994).

Although the Late Cretaceous theropod remains from Sudan, already mentioned in WERNER (1993a, 1994a), are very fragmentary, they provide new aspects on theropod evolution and paleogeography.

* Addresses of the authors: O. RAuHnT, Institut fiir Pal~iontologie, Freie Universit~it Berlin, Malteserstr. 74-100, Haus D, 12249 Berlin, Germany; Dr. C. WeRNEe,, SFB 69, TU Berlin, Ackerstr. 71-76, 13355 Berlin, Germany.

0031-0220/95/006940475 $ 3.75 �9 1995 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart

476 Oliver W. M. Rauhut & Christa Werner

Fig. 1. Location map of the vertebrate-bearing localities in Sudan. I: Wadi Milk Formation; lI: Shendi Formation. Abb. 1. Geographische Karte der Wirbeltier-Fundstellen im Sudan. I: Wadi Milk Formation; 1I: Shendi Formation.

Geological and palaeontological context

Cretaceous vertebrates of Sudan (Fig. 1) are known from the Shendi (WEmqER 1993b) and the Wadi Milk Formations (WERNER 1994a). The theropod fossils studied here come from the Wadi Milk Formation, which covers wide areas in Northern Sudan. The Wadi Milk Formation is dominated by sediments of braided rivers and sandy braided-meandering river systems (BuSSERT 1993). At the vertebrate locality, about 200 km north of Khartourn, the base of the outcropping part of the Wadi Milk Formation is represented by widely exposed fluviolacustrine sediments. This sedimentary sequence is interpreted as deposits of meandering rivers with dominating flood plain and lacustrine environments, minor fluviatile intercalation and rare paleosols (BosSERT 1993).

Based on results of paleoflora (LE3AL-NICOL 1987) and palynology (ScH~NK 1990; S C H ~ K & AWAD 1990), the Wadi Milk Formation was dated as Albian-Cenomanian in age. The stratigraphical interpretation of the vertebrates, in particular the presence of the fin spine and teeth ofAsteracanthus aegyptiacus STROMER 1927 at the base of the Wadi Milk Formation, suggests a Cenomanian age for the vertebrate-bearing layers (WEP, NER 1994a). This assumption is in good accordance with new palynological data from the Khartoum Basin (AWAD 1994). There the sediments of the upper parts of the Umrn Badda Member of the Omdurman For- marion, which are interpreted as a meandering river environment, are Cenomanian and late Cenomanian in age (AwAD 1994).

The fluvio-lacustrine sediments at the base of the Wadi Milk Formation (Fig. 1) yielded a rich continental vertebrate assemblage represented by non-articulated skeletal elements (WE~E~

First record of the family Dromaeosaurida (Dinosauria: Theropoda) 477

1994a). Fishes are abundantly present including polypterids, lepisosteids, osteoglossids, teleosts and lungfishes; cartilaginous fishes, however, are rare. The existence of amphibians is proven by frogs, caecilians (WE~'qER 1994b) and salamanders. Reptiles, as turtles, snakes (WE~'qER ~ RAGE 1994) and crocodiles, are documented by numerous species and specimens. Mammals have not been discovered, but a few lizard remains and mainly dinosaur bone fragments represent the terrestrial living elements of the Cretaceous fauna of Sudan. In the Wadi Milk Formation, the dinosaur assemblage comprises a titanosaurid sauropod, a hypsilophodontid and an iguano- dontid ornithopod, as well as theropods. The theropod material is relatively diverse, including fragments of a questionable ornithomimid and at least one larger form. Other selected theropod remains from the Cretaceous of Sudan are the subject of this study.

Material and methods The dinosaur remains of the Wadi Milk Formation, isolated teeth and postcranial elements, were col-

lected from the weathered surface. Due to the bad condition of most bones found, only a small quantity of the best preserved dinosaur remains were transported to the laboratory in Berlin for further study. The poor preservation of the large bones was caused by abrasion during fluvial transl~ort before sedimentation and recent fracturing and disintegration. In contrast to the large dinosaur material, the specimens described here represent relatively small-sized dinosaur elements, which show weak traces of transport. The material studiedand illustrated here comprises one tooth (Vb-875) and five phalangal elements (Vb-713, Vb-714, Vb-860, Vb-866 and Vb-868). They are deposited in the collection of the Special Research Project 69 of the Technical University of Berlin (TUB-SFB69).

In addition, the holotype of Deinonychus, stored in the Yale Peabody Museum, New Haven, and many unpublished theropod specimens housed in the Museum of the Rockies (MOR), Bozeman, Montana, were examined by one of the authors (O.R.).

The taxonomic value of theropod teeth was emphasised by CURRIE et al. (1990). Especially useful for taxa recognition, at least on the family level, are characters as serration morphology and denticle size differences between the anterior and posterior carinae.

Theropod teeth are often characterized by the number of denticles per given length (usually 1 or 5 ram) of the anterior and posterior carinae (e.g. OSTROM 1969b, CURRIE et al. 1990). Denticle size scales to tooth size (FARLO~ et al. 1991), making comparisons between theropod teeth of different sizes difficult. However, the ratio between the number of denticles for a certain distance of the anterior and posterior carinae, proposed here as "denticle size difference index" (DSDI), represents an index independent of tooth size. For DSDI calculation of several taxa, J. O. FARLOW kindly placed at our disposal unpublished data on theropod teeth, used for a study of theropod lateral teeth (FARLOW et al. 1991). The mean DSDI values are calculated from all available teeth data of one genus (Tab. 1). Due to DSDI variation within one genus, the variation range includes the highest and lowest values for single teeth of this genus (Tab. 2).

The values for T C H (= tooth crown height), FABL (= fore-aft basal length) and BW (Tooth basal width), as defined by CUF, RIE et al. (1990) and FARLOW et al. (1991) cannot be given for the incomplete Sudanese tooth. All systematic terms are used in the meaning of HOLTZ (1994).

Desc r ip t ion

T o o t h : Vb-875 is a nearly complete crown of a lateral tooth (Figs. 2a, 3a). The preserved part is 8.3 mm high, 6.5 mm long and 2.5 mm wide. The crown is strongly flattened and curved backwards. In cross-section, the tooth is slightly asymmetrical, the labial side being more convex than the lingual one. The tooth enamel is smooth.

The anterior and posterior serrations run down from the tip to the broken basal end of the crown. The basal anterior denticles are broken away. The anterior carina is very slightly bent to the lingual side. Both anterior and posterior denticles point apically, more strikingly so on the latter (Figs. 2b, 3b). The bases of the posterior denticles are relatively straight, while the tips


Fig. 2. A tooth of a dromaeosaurid theropod from the Upper Cretaceous of northern Sudan (Vbb875). a: labial view; b: magnification of the anterior (left) and posterior (right) serrations. Scale bars indicate 1 mm. Abb. 2. Ein Zahn eines dromaeosauriden Theropoden aus der Oberkreide des n6rdlichen Sudan (Vb-875). a: Labiale Ansicht; b: Vergr6flemng der mesialen (links) und distalen (rechts) Serrationen. Ma~st~ibe entsprechen 1 mm.

hook apically. There are 4 denticles per mm on the anterior carina and 3 denticles per mm on the posterior one, resulting in a DSDI value of 1.33. The anterior denticles are not only smaller than the posterior ones in respect of their basal length, they are also lower. No grooves are visible at the base of the denticles.

P h a I a n g e a I e 1 e m e n t s : The quite complete phalanx Vb-713 (Figs. 4a, 5a) is 36 mm long, 18 mm high, 15 mm wide at the proximal and 11 mm wide at the distal end.

Its proximal articular facet (Fig. 4a, left outline) shows two slightly asymmetrical concavities, separated by a vertical ridge. In proximal view, the left side is a little wider than the right one. The proximal end is characterised by a ventrally-situated proximal projection. This projection also takes part in the proximal articular facet. So, the ventral part of this facet exceeds the dorsal part proximally.

The distal articular facet (Fig. 4a, right outline) is narrower than the proximal one. It is developed as a deeply grooved ginglymus, that extends more proximally, ventrally than dorsally. The extension of the ginglymus allows an extensive dorso-ventral motion of the subsequent ungual, The collateral ligament fossae on the sides of the ginglymus are not deep, but large and sharp-edged dorsally. They are situated dorsal to the geometric centre of the ginglymus arc.

U n g u a I s : The ungual remains are fragmentary (Fig, 4b-e), all lacking the tips and Vb-860 and Vb-866 lacking the articular facet. Though broken distally, the ungual Vb-714 is the best preserved.

Vb-714 (Figs. 4b, 5b) and Vb-860 (Figs. 4c, 5c), when reconstructed, show equivalent di- mensions. In proximal view, Vb-714 is 28 mm high and 9 mm wide. The unguals are flattened laterally and strongly curved. While the narrow ventral border forms a sharp ridge, the dorsal one is rounded. In cross-section, the parts dorsal and ventral in respect to the claw grooves are subequal in width (Fig. 4b, c, cross-sections). In both specimens, the arrangement of the claw grooves is asymmetrical, the groove on one side being more ventral than on the other one (Figs. 4b, c; 5b, c). On both sides, an additional faint groove occurs in the proximal part dorsally to the actual claw groove; this character is more striking in Vb-714 than in Vb-860. The second grooves join the claw grooves distally from the levels of the flexor tubercles.


Fig. 3. SEM-pictures of the theropod tooth Vb-875. a: labial view; b: magnification of the anterior (left) and posterior (right) serrations. Scale bars indicate 1 mm. Abb. 3. REM-Aufnahmen des Theropoden-Zahnes Vb-875. a: Labiale Ansicht; b: Vergr61~erung der mesialen (links) und distalen (rechts) Serrationen. Mai~st~be entsprechen I ram.

The articular facet in Vb-714, which is 16 mm high and 9 mm wide, shows two concavities, divided by a vertical ridge (Fig. 4b, left outline). The flexor tubercle is large and only set off from the articular facet by a faint groove. A prominent ridge separates the tubercle from the blade of the claw. Above the articular facet, a small horizontal ridge indicates the insertion of the extension tendon.

The unguals Vb-866 (Fig. 4d) and Vb-868 (Fig. 4e), when reconstructed, are significantly smaller and less curved than the specimens described above. Their ventral parts, beneath the well developed claw grooves, are wider than the dorsal part. In Vb-866, both the ventral and the dorsal margins are rounded, in Vb-868, the ventral border is even flattened. The arrangement of the claw grooves is symmetrical in both specimens.

The articular facet of Vb-868, which is 9 mm high and 6 mm wide, is similar to that of Vb- 714, but the medial ridge is much less pronounced. The flexor tubercle is proportionally smaller in Vb-868 than in Vb-714.

Taxonomic implications To o t h: Strongly laterally compressed, recurved and sharply tapering teeth occur in the

maxillae and dentaries of many theropods, so these features are not diagnostic. As mentioned above, characters of taxonomic value are found in the serrations.

A striking feature of the Sudan tooth is the size difference between anterior and posterior denticles, giving a DSDI of 1.333. Ceratosaurs, allosaurids and tyrannosaurids, as well as the genera Carchorodontosaurus, Torvosaurus, Troodon and Dromaeosaurus show a DSDI of around 1 (Tab. 1). Higher DSDI were calculated for the teeth of some theropods of uncertain taxonomic position (Dryptosaurus, Richardoestesia, of. Richardoestesia) and for those of the dromaeosaurids Deinonychus, Velociraptor and Saurornitholestes, which show DSDIs over 1.5; the latter dromaeosaurid genera are members of the subfamily Velociraptorinae (sensu CURRIE et al. 1990). Compared with the mean DSDI values (Tab. 1), the DSDI of the Sudan tooth is


Fig. 4. Several phalangeal elements of a dromaeosaurid theropod from the Upper Cretaceous of northern Sudan in right lateral view. a: phalanx 1I-2 (Vb-713) with outlines of the proximal articular facet (left) and distal articular facet (right); b: ungual II-3 (Vb-714) with outline of the proximal end and cross section (below); c: ungual II-3 (Vb-860) with cross-section (below); d: ungual 7I-2 (Vb-866) with cross-section (right); e: ungual 7III-4 (Vb-868) with cross-section (right). All scale bars equal i era. Cross-sections and outlines are not drawn to scale. Abb. 4. Einige Phalangenelemente eines dromaeosauriden Theropoden aus der oberen Kreide des n6rd- lichen Sudan in rechter Lateralansicht. a: Phalange 1I-2 (Vb 713) mit Umrissen der proximalen (links) und distalen (rechts) Gelenkfl/iche; b: Knochenkralle II-3 (Vb-714) mit Umriss des proximalen Endes und Querschnitt (darunter); c: Knochenkralle 1I-3 (Vb-860) mit Querschnitt (darunter); d: Knochenkralle 7I-2 mit Querschnitt (rechts); e: Knochenkralle ?III-4 (Vb-868) mit Querschnitt (rechts). Alle Maf~sfiibe entsprechen 1 cm. Querschnitte und Umrisse sind nicht dem Maf~stab entsprechend.

closest to that of Richardoes~esia. The denticles in the teeth of Richardoestesia are of smaller size in relation to tooth size, and the teeth are more Ianceolate in shape (C~RgIe et aI. 1990).

In addition to the mean values (Tab. 1), the variation range of the DSDI (Tab. 2) allows more detailed conclusions. Looking at the variation ranges, the Sudanese tooth lies within the ravage of Richardoestesia, Deinonychus and Saurornitholestes. Due to the differences in tooth morphology mentioned above, a close relationship to Richardoestesia can be excluded. Considering the shape of the denticles, apically pointing posterior denticles occur in the teeth of the troodontid Troodon (CURRIE 1987) and the velociraptorine dromaeosaurids Deinonychus (OsTROM 1969b) and Saurornitholestes (C~SRRIE et al. 1990). Troodontid teeth are clearly distinguishable by larger denticle size in relation to tooth size and the presence of distinctive "blood pits" at the basis of the denticles (CURRIE 1987). The exact shape especially of the posterior denticles of the Sudanese tooth corresponds very well to that of the teeth of Deinonychus (OsTRO~ 1969b: fig. 25) and Saurornitholestes (CuRRIE et al. 1990: figs. 8.2; 8.7 E, H).

Summed up, the size and shape of the tooth and its denticles as well as the DSDI data indicate the existence of a velociraptorine dromaeosaurid theropod in the Cretaceous of Sudan.


Fig. 5. Photographs of the dromaeosaurid phalangeal elements Vb-713 (a), Vb-714 (b) and Vb-860 (c) in left lateral view. Note the differences in the arrangement of the claw grooves of Vb-714 and Vb-860 when compared to Fig. 4b, c. Scale bar equals 1 cm. Abb. 5. Photographien der dromaeosauriden Phalangenelemente Vb-713 (a), Vb-714 (b) und Vb-860 (c). Man bemerke den Unterschied in der Lage der Krallengrube bei Vb-714 und Vb-860 im Vergleich mit Abb. 4b, c. Ma~stab entspricht 1 cm.

P h a 1 a n g e a 1 e 1 e m e n t s : Two of the bones discussed here (Vb-713, Vb-714) were already figured as Deinonychus-like by WEBER (1994a: pl. 4, figs. 4, 5).

Manual phalanges of theropod dinosaurs are usually elongate and often lack a prominent vertical ridge on the proximal articular facet (e. g. OSTROM 1969b; MADSEN 1976). Therefore, the stout shape and the presence of a vertical ridge at the proximal articular facet in Vb-714 indicates that this specimen is a pedal phalanx (although a vertical ridge is also found in at least one manual phalanx of several theropods; VARRICCHIO, pers. com.).

The most striking feature of this pedal phalanx is a proximal projection of the ventral part of the proximal articular facet. A "heel" like that is typical for the second phalanx of the second pedal digit of troodontids and dromaeosaurids (OsTRoM 1969b; BARS~OLD 1983). Since this character is not found in any other theropod pedal phalanx, Vb-713 is thought to represent a second phalanx of the second pedal digit within troodontids or dromaeosaurids. This phalanx is compressed proximal-distally in all troodontids (RussELL 1969: fig. 14; OSM6LS~ 1987: fig. 3), with the exception of an undetermined Lower Cretaceous form (BARsBoLD et al. 1987, figured in OSM6LS~ ~ BARSl3OLO 1990: fig. 11. 2G). In contrast, the phalanx from Sudan is not compressed and has more typical theropod proportions with a distinctive "neck" between the distal and proximal articular facets. In this way, the phalanx is more similar to those found in dromaeosaurids.

Despite minor differences in the ventral "heel" and collateral ligament fossae, Vb-713 is quite similar to the phalanx 11-2 of Deinonychus antirrhopus in its general shape and morphology of the articular facets (OsTRo~ 1969b).

Therefore, the Sudanese specimen most probably represents a second phalanx of the second pedal digit of a dromaeosaurid theropod.

U n g u a l s : At first sight, the unguals Vb-714 and Vb-860 seem to represent theropod manual claws.

In contrast to the Sudan specimens, the enlarged manual ungual of the theropod Baryonyx (Fig. 6A) is not laterally compressed and the ventral part seems to be wider than the dorsal one


Tab. 1: The number of denticles per 5 mm on the anterior and posterior carinae and the relation between anterior and posterior serrations (DSDI) in several theropods. Data taken from FARLOW et al. (1991) and * OSTROM (1969b).

Tab. 1: Die Anzahl der Dentikel auf 5 mm der mesialen und distalen Carina und die Relation zwischen den Serrationen (DSDI) bei einigen Theropoden. Die Daten stammen von FARLOW et al. (1991) und * OSTROM (1969b).

Taxon: anterior carina posterior carina Number of teeth DSDI denticles/5 mm denticles/5 mm of which data

was available

Ceratosauria: Coelophis 40-60 40-55 6 1.052 Ceratosaurus* 10 i 0 ? 1.0

Allosauridae: Allosaurus* 10-12 10-12 ? 1.0

Theropoda inc. sed.: Torvosaurus 6 7 1 0.857 Drpytosaurus 15 10 1 1.5 Richardoestesia 30-50 24-32.5 7 1.247 cf. Richardoestesia 35-40 20-45 2 1.705 Carcharodontosaurus 10 12 I 0.833

Tyrannosauridae: Albertosaurus 8 8.5 1 1.063 Daspletosaurus 12 12 1 1.0 Tyrannosaurus 6-10 6-12 18 0.965 Tarbosaurus 7 7 2 1.0 Aublysodon 14-19 12-18 10 1.043 Alectrosaurus 13-14 14-16 3 0.911 ? Nanotyrannus 14 14 1 1.0

Troodontidae: Troodon 4.7-10.7 6.8-9.4 10 0.94

Dromaeosauridae: Dromaeosaurus 13-20 14-17 10 1.025 Deinonychus 21-35 14-17 19 1.749 Velociraptor* 38-40 25-26 ? 1.529 Saurornitholestes 25-45 20-25 9 1.571

Sudan theropod 20 15 1 1.333

Tab, 2: The variation range of the DSD! for some theropod genera, of which data was available for more than five teeth. Data taken from FARLOW et al. (1991),

Tab. 2: Die Variationsbreite des DSDI bei einigen Theropodengattungen, bei denen Daten ffir mehr als ffinf Z~ihne vorlagen. Die Daten stammen von FARLOW et al. (1991).

Genus: Variation range Genus: Variation range of of DSDI: DSDI:

Coelop hysis 0.9-1.2 Troodon 0.603-1.138 Richardoestesia 1.065-1.538 Dromaeosaurus 0.813-1.176 Tyrannosaurus 0.778-1.167 Deinonych us 1.313-2.333 Aublysodon 0.941-1.188 Saurornitholestes 1.19-2.0


d d

d

Fig. 6. Manual unguals of several theropod dinosaurs. A: ungual of digit ?I of Baryonyx; B: ungual II of Allosaurus; C: ungual II of GaUimimus; D: ungual II of Compsognathus; E: ungual ?I of Elmisaurus; F: un~nal II of Chirostenotes; G: ungual I of Oviraptor; H: ungual III of Saurornitbolestes; I: ungual II of Vetociraptor; K: ungual II of Deinonychus. Note the "depression" (d) between articulation facet and claw blades in several coelurosaurian theropod unguals. Drawn to the same hight of the articulation facet. Scale bars equal 1 cm (D, E, F, G, H, I) and 5 cm (A, B, C, K). (Redrawn after A: CHARIG & M1LNER 1990; B: Madsen 1976; C, G, I: BARSBOLD 1983; D: OSTI~OM 1978, reversed; E: OSM6LSKA 1981; F: CURRIE & RUSSELL 1988; H: SUES 1978; K: OSTROM 1969b, reversed).

Abb. 6. Knochenkrallen der Hand einiger Theropoden. A: Kralle ?I von Baryonyx; B: Kralle II yon AI- losaurus; C: Kralle II yon GaUimimus; D: Kralle II von Compsognathus; E: Kralle ?I von Elmisaurus; F: Kralle II von Chirostenotes; G: Kralle II von Oviraptor; H: Kralle III von Saurornitholestes; I: Kralle II von Velociraptor; K: Kralle II von Deinonychus. Man beachte die Einbuchtung (d) zwischen der Artikulations- Facette und dem Krallenk6rper bei mehreren Coelurosauriern. Alle Krallen auf dieselbe H6he der Ar- tikulations-Facette gezeichnet. Maf~st~ibe entsprechen 1 cm (D, E, F, G, H, I) und 5 cm (A, B, C, K). (Nachgezeichnet nach A: CHARIG & MILNER 1990; B: MADSEN 1976; C, G, I: BARSBOLD 1983; D: OSTROM 1978, spiegelverkehrt; E: OSM6LSKA 1981; F: CURRIE & RUSSELL 1988; H: SUES 1978; K: OSTROM 1969b, spiegelverkehrt).


(CHARIG & MILNER 1990). Since Spinosaurus is closely related to Baryonyx (Bu~rETAUT 1992), it is unlikely that the claw from Sudan represent a small or juvenile spinosaur. The manual unguals of Allosaurus (Fig. 6B) are not compressed and the arrangement of the claw grooves is symmetrical (MaI)s~ 1976). The flexor tubercle is placed more distally than in Vb-714. A manual claw assigned to Carcharodontosaurus (LAvvARENT 1960: pl. 6, fig. 13) significantly differs from the Sudan specimens in being almost as high proximally as it is long.

The manual claws of the primitive coelurosaurian theropods Ornitholestes (OsBoRN 1903) and Compsognathus (Fig. 6D; OsrRo~ 1978) are only slightly curved and the position of the flexor tubercle is different from Vb-714.

In the manual unguals of the more advanced coelurosaurian theropod taxa Oviraptorosauria, Ornithomimosauria, Elmisauridae and Dromaeosauridae (Fig. 6C, E-K), the articular facet exceeds the ungual blade in height, giving the appearance of a dorsal depression between the articular facet and the claw blade (GIL~ORr 1924: fig. 1; OSl3ORN 1924: fig. 2; OST~OM 1969b: fig. 63; SuEs 1978: pl. 5; OSMOLSKA 1981: fig. 1; BARSBOLD 1983: fig. 21b; CURRIE & RUSSELL 1988: fig. 4). The only known manus of a troodontid is that of Sinornithoides, which has not been described in detail yet (RusSELL & DONG 1993), but isolated manual unguals of Troodon formosus seem to show the same characters (Vm~RICClO, pers. com.). In the tyrannosaurid theropod Albertosaurus, at least the ungual of the first digit seem to show a "depression" between articular facet and claw blade (LAMBE 1917: fig. 35 A, B). Furthermore, the flexor tubercle in the manual unguals of Albertosaurus is placed more distally than it is in the specimens from Sudan. This is also the case in ornithomimosaurs (Fig. 6C), where the manual unguals are only slightly curved or even straight (BARsBOLr) & OSM6LSKa 1990).

A supposed manual ungual of Utahraptor (KIgKLAND et al. 1993: fig. 11) does not show the characters usually found in advanced coelurosaurian manual unguals, but rather resembles dromaeosaurid second pedal unguals. Due to the differences from theropod manual unguals, the specimens from Sudan most probably represent pedal elements.

In many theropods, the pedal unguals are flattened ventrally and only slightly curved (e. g. OSTROM 1969b: fig. 80a, b,h; MADSEN 1976: pl. 54). Strongly curved and laterally compressed claws are known in the pes of dromaeosaurids, troodontids (Fig. 7B-F) and Noasaurus. The claw of Noasaurus differs significantly from the Sudanese unguals in showing a groove rather than a tubercle as insertions area of the flexor tendon and in having a wide articular facet (BoNAPARVE & POWELL 1980: fig. 8E, F). The enlarged pedal unguals of troodontids show a second claw groove dorsally to the normal one on the proximal part of the claw, which joins the main claw groove distally (RusSELL 1969: figs. 14, 15; OSM6LSICa 1987: fig. 3). This character, which is found in both specimens from northeastern Africa, has also been observed in an undescribed second pedal claw of a dromaeosaur, probably Saurornitholestes (MOR 660). In this specimen, though, the angle between the two grooves is much more acute than it is in troodontids (VAI~RICCmO, pers. com.). In the Sudan unguals, the angle is intermediate between the condition found in Troodon and MOR 660.

The degree of curvature of the second pedal unguals of troodontids and dromaeosaurids is subject to variation. In troodontids, Borogovia exhibits a nearly straight claw (OSM6LSKA 1987), while Troodon shows a strongly curved one (RusSELL 1969); the extremes in dromaeosaurids are Adasaurus (BARsBOLD 1983) and Deinonychus (OsTROM 1969b), respectively.

In dromaeosaurids, the flexor tubercle of the second pedal ungual is situated at the proximal end of the bone (OSTROM 1969a, b; BA~S13OLD 1983), but in troodontids, the position of this tubercle may vary (RUSSELL 1969: figs. 14, 15B).

Theropod pedal unguals are usually rounded ventrally, even the second pedal unguals of troodontids (VARRICCIqIO, pers. com.). A sharp ventral margin, as it is found in the Sudanese specimen, is elsewhere only found in dromaeosaurids.

An asymmetrical arrangement of the claw grooves is present in the second pedal unguals of Utahraptor (KIRKLAND et al. 1993), Deinonychus (pers. obs.; OSTROM 1969a: figs. 1, 2a) and in


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Fig. 7. Penultimate phalanx and ungual of the IIIrd (A) and Ilnd (B-G) digit of the pes of several theropods. A: Allosaurus; B: undetermined troodontid from the Lower Cretaceous of Mongolia; C: Troodon; D: Adasaurus; E: Velocirapto~, F: Deinonychus; G: Sudan dromaeosaurid, reconstructed after Vb-713, Vb- 714 and Vb-860. Drawn to the same length of the phalanx. Scale bars indicate 1 cm (B, C, D, E, G) and 5 cm (A, F). (Redrawn after A: MADSEN 1976; B: OSM6LS~ ~ BARSBOLD 1990; C: RUSSELL 1969, reversed; D: BA~SBOLD 1983; E, F: OSTROM 1969b, reversed). Abb. 7. Vorletzte Phalange und Kralle der III (A) und II (B-G) Zehe des Fuf~es verschiedener Theropoden. A: Allosaurus; B: Unbestimmter Troodontide aus der Unterkreide der Mongolei; C: Troodon; D: Ada- saurus~E: Velociraptor, F: Deinonychus; G: Sudan-Dromaeosaurid, rekonstruiert nach Vb-713, Vb-714 und Vb-860. Auf dieselbe L~nge der Phalange gezeichnet. Mat~sfiibe entsprechen 1 cm (B, C, D, E, G) und 5 cm (A, F). (Nachgezeichnet nach A: MADSEN 1976; B: OSM6LS~ ~ BARSBOLD 1990; C: RUSSELL 1969, spiegelverkehrt; D: BARSBOLD 1983; E, F: OST~OM 1969b, spiegelverkehrt).


an undescribed dromaeosaurid (MOR 660). This feature has not been described or observed in any other theropod ungual, and is therefore interpreted here as being unique in dromaeosaurids. Since this diagnostic character is found in both specimens from Sudan, they consequently represent a dromaeosaurid theropod.

The African claws Vb-866 and Vb-868 show a morphology as it is generally found in theropod pedal unguals and are of an appropriate size to be linked to the other pedal elements from Sudan discussed here. Looking at the pes of Deinonychus (OsTROM 1969b), Vb-868 is equivalent to the ungual of the third digit, while Vb-866 may be a claw from the first digit.

Summed up, the following characters link the material from Sudan to the family dromaeosauridae:

- The difference between denticle size of the anterior and posterior serration in the tooth Vb-875 in combination with the morphology of the posterior serrations.

- The prominent ventral "heel" and the deeply grooved ginglymoidal distal articular facet of the pedal phalanx Vb-713.

- The shape of the unguals Vb-714 and Vb-860 in combination with a asymmetrical arrangement of the claw grooves and a sharp ventral margin.

Because of the well corresponding size and morphology of the Sudanese phalangeal elements, they are interpreted to represent the same taxon.

Given the combination of the tooth and the pedal elements, the presence of a dromaeosaurid theropod in the Late Cretaceous of Sudan is most likely. The morphology of the tooth allows the reference of the African taxon to the subfamily Velociraptorinae.

Due to the differences in the phalange Vb-713 and the unguals Vb-714 and Vb-860 to the same elements in other dromaeosaurids, the material from Sudan surely represents a new genus and species, but because of the very fragmentary nature of the remains, no new name is proposed here.

P a l e o b i o g e o g r a p h i c a s p e c t s

Until now, dromaeosaurid theropods were known only from Cretaceous sediments of the northern hemisphere. The earliest occurrence of dromaeosaurs is recorded from the Barremian of Utah (KIRI~LAND et al. 1993). Several articulated skeletons of Deinonychus antirrhopus were described from the Aptian-Albian of Wyoming and Montana (OsTROM 1969a, b). Dromaeo- saurids may also be present in the Aptian-Albian of Asia (WEISHAMPEL 1990: p. 105, #248). Velociraptor mongoliensis OSBORN 1924, documented by several skeletons as well, is known from the late Santonian or early Campanian from the Mongolian People's Republic and People's Republic of China (OsTROM 1990). In the Campanian Judith River Formation of Canada and Montana, two dromaeosaurid genera are present: Dromaeosaurus MATTHEW & BROWN 1922 and Saurornitholestes SUES 1978; apart from skeletal remains, both genera are also represented by numerous teeth (CuRRIE et al. 1990; FIORILLO & CORRIE 1994). The Campanian and early Maastrichtian strata of the Mongolian People's Republic yielded the youngest dromaeosaurid fragments of Asia to date (OSM6LSr~ 1982; BARSBOLD 1983). Different claims for the presence of dromaeosaurids in the Late Cretaceous of southern Europe have been made (BuFF~TA~T et al. 1986; ANTUNES & SIGOGNEAU 1992). While there are good arguments that the teeth described by BUFFETAUT et al. (1986) represent dromaeosaurids, the specimen from Portugal is questionable (ANTUNES & SIGOGNEALI 1992). Some theropod fragments from the Maastrichtian of Romania, originally described by GmGORESU et al. (1985) as "Coelurosaurians", have been interpreted as dromaeosaurid (BUFFETAUT et al. 1986). Dromaeosaur-like teeth from the Barremian of Spain indicate the presence of this family in the Lower Cretaceous of Europe, as well (pers. obs.).

The occurrence of dromaeosaurid remains in the Cretaceous of Sudan represents the first record of this theropod group in Gondwanian continents. The origin of the family Dro-


maeosauridae is not proven by the evidence of fossils. OSTROM (1990) proposed a North American ancestor close to the small Late Jurassic theropods Coelurus and Ornitholestes. On the other hand, there seems to be a close phylogenetic relationship between dromaeosaurids and the primitive bird Archaeopteryx from the Late Jurassic of Europe (OsTROM 1976; GAUTHIER 1986; HOLTZ 1994). Considering this relationship, an Early to Middle Jurassic origin of the Dromaeosauridae, possibly in Europe, is likely.

Since there is good evidence for a faunal interchange between Europe, North America and Africa in the Late Jurassic (GALTON 1977, 1982), the dispersal of early dromaeosaurs among these continents could well have taken place during this period, too.

Another possibility for the spreading of different dromaeosaurid lineages may be a connection between Africa and Europe in the Lower Cretaceous, as proposed by GALTON ~ TA- QUET (1982) and MILNER & NORMAN (1984).

A final paleobiogeographic conclusion is not yet possible due to the lack of fossil evidence, especially in Europe and Africa. However, the first record of a dromaeosaurid theropod in the Cretaceous of a Gondwanian continent proves a wider distribution and diversification of this group in Cretaceous times, than known before.

Acknowledgements

We would like to thank the German Research Foundation for financial support of the work. Special thanks are due to Dr. JAMES O. FARLOW, Fort Wayne, for providing unpublished data on theropod teeth and to DAvm VARRICCmO, Bozeman, for useful information on unpublished material. Dr. BERNARD KREBS, Berlin, Dr. JAMES O. FARLOXV, Fort Wayne and DAVID VARRICCHIO, Bozeman, are thanked for critical comments on the manuscript. O.R. is indebted to Dr. JOHN H. OSTROM, New Haven, as well as DAWD VARRICCmO and Dr. JAcK HORNER, both Bozeman, Montana, for giving assistance in the studying specimens from their respective collections.

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Eingang des Manuskriptes am 28. November 1994; Annahme durch die Schrlftleitung am 7. Dezember 1994.

First record of the family Dromaeosauridae (Dinosauria: Theropoda) in the Cretaceous of Gondwana (Wadi Milk Formation, northern Sudan)

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