Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 19-44 10.11.2002

Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania)

Martin Aberhan ', Robert Bussert2, Wolf-Dieter Heinrich', Eckhart Schrank2, Stephan Schultkal, Benjamin Sames3, Jiirgen =wet4 & Saidi Kapilima5

With 6 figures, 2 tables, and 2 plates

Abstract

The Late Jurassic to Early Cretaceous Tendaguru Beds (Tanzania, East Africa) have been well known for nearly a century for their diverse dinosaur assemblages. Here, we present sedimentological and palaeontological data collected by the German- Tanzanian Tendaguru Expedition 2000 in an attempt to reconstruct the palaeo-ecosystems of the Tendaguru Beds at their type locality. Our reconstructions are based on sedimentological data and on a palaeoecological analysis of macroinverte- brates, microvertebrates, plant fossils and microfossils (ostracods, foraminifera, charophytes, palynomorphs). In addition, we included data from previous expeditions, particularly those on the dinosaur assemblages. The environmental model of the Tendaguru Beds presented herein comprises three broad palaeoenvironmental units in a marginal marine setting: (1) Lagoon-like, shallow marine environments above fair weather wave base and with evidence of tides and storms. These formed behind barriers such as ooid bar and siliciclastic sand bar complexes and were generally subject to minor salinity fluctuations. (2) Extended tidal flats and low-relief coastal plains. These include low-energy, brackish coastal lakes and ponds as well as pools and small fluvial channels of coastal plains in which the large dinosaurs were buried. Since these environments apparently were, at best, poorly vegetated, the main feeding grounds of giant sauropods must have been elsewhere. Presumably, tidal flats and coastal plains were visited by dinosaurs primarily during periods of drought. (3) Vegetated hinterland. Vegetation of this environment can only be inferred indirectly from plant material transported into the other depositional environments. Vegetation was dominated by a diverse conifer flora, which apparently formed part of the food source of large herbivorous sauropods. Evidence from various sources suggests a subtropical to tropical palaeocli- mate, characterised by seasonal rainfall alternating with a pronounced dry season during the Late Jurassic. In Early Cretac- eous times, sedimentological and palaeontological proxies suggest a climatic shift towards more humid conditions.

Key words: Tendaguru, Tanzania, Mesozoic, Jurassic, sedimentology, palaeozoology, palaeobotany, palynology, palaeoecology, taphonomy, dinosaurs, climate

Zusammenfassung

Die Tendaguru-Schichten von Tansania in Ostafrika (Oberjura bis Unterkreide) sind als Lagerstatte obejurassischer Dinosau- rier seit nahezu einem Jahrhundert weltweit bekannt. Anhand von sedimentologischen und palaontologischen Daten, die wah- rend der Deutsch-Tansanischen Tendaguru Expedition 2000 im Typus-Gebiet der Tendaguru-Schichten gewonnen wurden, werden Palao-Okosysteme rekonstruiert. Grundlage der Rekonstruktionen sind die Auswertung sedimentologischer Daten sowie die palao-okologische Analyse von Makroinvertebraten, Mikrovertebraten, pflanzlichen Fossilien und Mikrofossilien (Ostrakoden, Foraminiferen, Charophyten, Palynomorphen). Dariiber hinaus werden Informationen uber Dinosaurier beriick- sichtigt, die bei friiheren Expeditionen gewonnen wurden. Das hier vorgestellte Ablagerungsmodell der Tendaguru-Schichten umfaat drei Teilbereiche eines randlich marinen Sedi- mentationsraumes, die wie folgt gekennzeichnet werden konnen: (1) Lagunen-artige, marine Flachwasserbereiche, die ober- halb der Schonwetter-Wellenbasis lagen und unter deutlichem Einflul3 von Gezeiten und Sturmen standen. Sie waren vom offenen Meer durch Barrieren, wie Ooidbarren und siliziklastischen Sandbarrenkomplexen, getrennt und wiesen einen leicht schwankenden Salzgehalt auf. (2) Ausgedehnte Wattgebiete und flache Kustenebenen. Dort befanden sich niedrig-energeti- sche, brackische Strandseen und Teiche sowie Tiimpel und kleinere FluBrinnen, in denen die groBen Dinosaurier eingebettet wurden. Da diese Lebensraume bestenfalls durftig bewachsen waren, mussen die Nahrungsquellen und der eigentliche Le- bensraum der riesigen Sauropoden anderswo gelegen haben. Vermutlich wurden die Wattgebiete und Flachkiisten von Dino-

Museum fiir Naturkunde, Zentralinstitut der Humboldt-Universitat zu Berlin, Institut fiir Palaontologie, Invalidenstr. 43, D-10 115 Berlin, Germany. E-mail [email protected] Institut fiir Angewandte Geowissenschaften, Technische Universitat Berlin, Sekr. BH 2, Emst-Reuter-Platz 1, D-10587 Berlin, Germany. Institut fiir Geologische Wissenschaften, Fachrichtung Palaontologie, Freie Universitat Berlin, Malteserstr. 74-100, D-12249 Berlin, Germany. Department of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 lRJ, United Kingdom. Department of Geology, University of Dar es Salaam, PO. Box 35052, Dar es Salaam, Tanzania. Received March, accepted July 2002

0 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1435-1943/02/0511-0019$17.50+.50/0 20 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds sauriern vorrangig in den Trockenzeiten aufgesucht. (3) Bewachsenes Hinterland. Die Vegetation dieses Lebensraumes kann nur indirekt aus Pflanzenresten erschlossen werden, die in die anderen Ablagerungsraume transportiert wurden. Die Vegeta- tion wurde von einer diversen Koniferenflora dominiert, die zumindest teilweise die Nahrungsgrundlage der groRen, herbivo- ren Sauropoden bildete. Sedimentologische und palaontologische Indikatoren sprechen fir ein subtropisches bis tropisches Klima wahrend der spaten Jurazeit mit einem jahreszeitlichen Wechsel von Regenfallen und ausgepragten Trockenzeiten. In der friihen Kreidezeit deutet sich ein Wechsel zu starker humiden Bedingungen an.

Schliisselworter: Tendaguru, Tansania, Mesozoikum, Jura, Sedimentologie, Palaozoologie, Palaobotanik, Palynologie, Palaoo- kologie, Taphonomie, Dinosauner, Klima

Introduction Geological setting and study area

The famous fossil locality of Tendaguru is lo- The Tendaguru area is situated in the southwest cated approximately 60 kilometers northwest of of the Mandawa Basin, a coastal basin forming the seaport of Lindi in southeastern Tanzania. the southwestern part of the Somali Basin. The While the diverse Late Jurassic dinosaur assem- Masasi Basement Complex marks the western blages of the Tendaguru Beds have attracted boundary of the Mandawa Basin. To the south, a considerable scientific attention (e.g., Maier in basement uplift separates this basin from the Ru- press), many associated organisms such as micro- vuma Basin, while the northern boundary is vertebrates, plants and microfossils (e.g., ostra- formed by the Rufiji Basin (TPDC 1995). cods and palynomorphs) remain largely un- The Mesozoic sediments of the Mandawa Ba- known. Only the Late Jurassic to Early sin record plate tectonic processes related to the Cretaceous macroinvertebrates (mainly molluscs break-up of Gondwana. During the Permo-Trias- and corals) are well documented in the literature sic, far-field stresses associated with the Gondwa- (e.g., Hennig 1914a, Lange 1914, Zwierzycki nide orogeny promoted the reactivation of pre- 1914, Dietrich 1914, 1926, 1933, Cox 1965), and existing fracture systems and the development of a quantitative palaeoecological analysis together the intracratonal Karoo rifts (Visser & Praekelt with a modern sedimentological analysis of the 1996, Trouw & De Wit 1999). The Early Jurassic Tendaguru Beds is still lacking. continental siliciclastic sediments of the Manda- In order to fill this gap in our understanding wa Basin indicate the presence of at least the of the Tendaguru ecosystem, an expedition revis- youngest part of the Karoo system (Balduzzi ited Tendaguru in 2000 (Heinrich et al. 2001) et al. 1992). with the aim of collecting new sedimentological Subsequently, the onset of sea-floor spreading and stratigraphical data, invertebrates, microver- in the Somali basin and the initial disintegration tebrates and plant fossils. In this paper, we com- of Gondwana during the Middle Jurassic re- bine sedimentological and palaeontological data sulted in a break-up unconformity (Kreuser in an attempt to reconstruct the environmental 1995) and in a marine transgression that reached setting of the Tendaguru Beds at their type local- the Mandawa Basin from the north. The basin ity. For this purpose, the six lithostratigraphic developed into a passive continental margin and units of the Tendaguru Beds were analysed sepa- entered a sag phase. During the Late Jurassic, a rately so that stratigraphically less constrained northeast dipping continental to shallow marine information from former expeditions, particularly ramp setting was established, with a mixed car- the German Tendaguru Expedition (1909-1913, bonate-siliciclastic sedimentation that probably GTE) could be included. For each unit, we pre- continued until the Valanginian - Hauterivian. sent a brief outline of the overall lithology and The cyclic character of the Late Jurassic to early sedimentary structures, followed by a description Early Cretaceous sediments suggests control by of the macroinvertebrates and calcareous micro- sea-level changes. In Early Cretaceous times, an fossils, macro- and microvertebrates, and meso- unconformity developed in response to a wide- and palynoflora. This information is utilized for spread phase of regression and uplift that might environmental and palaeoecological interpreta- be related to the end of spreading in the Somali tions of the various litho- and biofacies. Finally, Basin (Coffin & Rabinowitz 1988) and/or the on- an attempt was made to develop an integrated set of separation between MadagascadIndia, environmental model of the Tendaguru Beds in Australia and Antarctica (Powell et al. 1988). In the light of these new results. the late Early Cretaceous, deposition continued with fluvial to shallow marine siliciclastic sedi- ments of the Makonde Formation. Mitt. Mus. Nat.kd. Berl.. Geowiss. Reihe 5 (2002) 21

Fig. 1. Geological map of the Tendaguru area with location of profiles and samples. Bol: Bolachikombe; Dwa: Dwanika; Kin: Kindope; Kit: Kitukituki; Kor: coral locality; Mai: Maimbwi; Tin: Tingutinguti. Based on Hennig (1914a), Janensch (1914a, b, 1925a) and new data of the German-Tanzanian Tendaguru Expedition 2000. Aberhan, M. et al., Palaeoecology of the Tendaguru Beds

Microin- Macroin- Microflorz Mesoflora Vertebrates ertc ate: ebr

E -0u) -u) Uu) 8 u) 3 -> 8 0 0 L !.! m cP I 'E ._ 3 E n - -0 -,o - -m0)

Upper Saurian Bed + * * + + + + +

70

+ * * 80 Trigonia srneei + + * Bed + + + + + + + + * + * * 50

+ + 40 + Middle + $ Saurian Bed + + * + + * + +

+ +

+ + + + 10 * i + + + + + + + + Mitt. Mus, Nat.kd. Berl., Geowiss. Reihe 5 (2002) 23

In the Paleogene and Neogene, the western Cuticles were prepared according to standard procedures. Fossil plant-bearing rocks were bulk-macerated in 45 YO hy- part of the Mandawa Basin experienced several drofluoric acid, washed with distilled water, macerated using phases of uplift, whereas the eastern part contin- Schulze’s reagent (HN03 and KC103) and rinsed with KOH. ued to subside (Kent et al. 1971). Finally, tilting After gentle dehydration in pure glycerine, cuticles were mounted on slides using glycerine-jelly. Fusain was mechani- and erosion of the sedimentary sequence re- cally prepared using steel needles or obtained by sieving sulted in a general outcrop pattern consisting of after disaggregation of samples with water or H202. Subse- Late Jurassic deposits to the west, Cretaceous se- quently, the fusain was mounted on SEM stubs, coated with gold-palladium and examined using a Jeol JMS 6300 elec- diments in the centre of the basin, and the tron-microscope. youngest strata along the coast. The fossil material figured in Plates 1-2 is housed at the In the Tendaguru area, the Late Jurassic to Museum fur Naturkunde, Humboldt Universitat Berlin (h4B.) and the Institut fur Angewandte Geowissenschaften, Early Cretaceous Tendaguru Beds are well ex- Technische Universitat Berlin (IY). posed in several small streams in the vicinity of Tendaguru Hill, especially at Tingutinguti, Dwanika and Maimbwi (Fig. 1). The Lower Stratigraphy Saurian Bed is largely buried under deposits of the Mbwemkuru floodplain, and only the basal In the type area, the Tendaguru Beds (Janensch part of the Trigonia schwarzi Bed can be seen, 1914b) lie unconformably on Proterozoic base- exposed at the top of Tendaguru Hill. ment rocks and reach a thickness of approxi- mately 110 m. Three fine-grained dinosaur-bear- ing sequences (Lower, Middle and Upper Methods Saurian Beds), each 10-30m thick, are interca- lated with sandstone-dominated sequences con- This study focuses on our own bed-by-bed compilation of palaeontological and geological data for the Tendaguru area taining a predominantly marine fauna and reach- (Fig. 2). Stratigraphically less constrained information from ing thicknesses of up to 30m (Nerinea Bed, previous expeditions was included where appropriate. In par- Trigonia smeei Bed, Trigonia schwarzi Bed) ticular, this concerns the dinosaur assemblage, since renewed excavations of large vertebrates were not part of the current (Fig. 2). These six main stratigraphic intervals project. The topographic location of the dinosaur-bearing probably correspond to the modern stratigraphic sites of the GTE were described by Janensch (1914a, 1925a) equivalent of members, but are not formally de- and Heinrich (1999a). Several sections of the Tendaguru Beds were measured sedimentologically, and 187 sediment fined here, pending further studies. The term samples were taken back to the laboratory. Their bulk com- Tendaguru Formation has been proposed by position was estimated by X-ray diffraction (XRD) analyses Schudack (1999), but has not yet been formally of non-oriented powder samples. Clay mineral analyses were carried out on textured mounts from selected samples. Data defined or described. Towards the east, the thick- on the chemical composition were obtained from X-ray fluor- ness of the sandstone-dominated sequences in- escence. The microfacies of sediments was investigated by creases, whereas those of the Saurian beds de- optical microscopy of thin sections. Quantitative biostratinomic data for macroinvertebrates creases (Hennig 1937). Laterally, the siliciclastic were collected in the field. Fossiliferous bulk samples were sediments of the Trigonia srneei Bed interfinger taken from single layers of uniform lithology. These were with carbonates. The sandstones of the Tenda- mechanically disaggregated to obtain the macroinvertebrate fauna, which, where possible, was then analysed using statis- guru Beds are rich in feldspars and the matrix tical techniques. To recover microfossils (microvertebrates, consists mainly of calcite. The clay mineral frac- juveniles of molluscs, ostracods, foraminifera, charophytes), tions are dominated by smectite and illite. By the samples were first treated with warm water andor HzO2. Microvertebrate samples were also treated with acetic acid contrast to the sandstones of the Nerinea and the (about 5% by volume). The residues obtained were washed Trigonia smeei Bed, the sandstones of the Trigo- with water through a mesh, dried and hand-sorted using a nia schwarzi Bed have higher potassium feld- binocular microscope. The intensive weathering of surface material often ham- spar/plagioclase feldspar-ratios. Altogether, ten pers palynological investigations in tropical areas. Therefore lithofacies types were identified. They are sum- every effort was undertaken to obtain fresh samples. Labora- marized in Table 1 and discussed below. tory processing of samples involved the usual HCUHF extrac- tion and 15 pm sieving, but oxidation of the acid-resistant The biostratigraphy of the Tendaguru Beds has residues was avoided. been much debated, but a Late Jurassic to Early

4 Fig. 2. Composite section of the Tendaguru Beds in the type area with stratigraphic position of samples and distribution of major fossil groups within the section. For geographical location of samples and their abbreviations see Fig. 1. Based on new data of the German-Tanzanian Tendaguru Expedition 2000. 24 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds

Table 1 Lithofacies types for the Tendaguru Beds and their interpretation lithofacies lithology sedimentary structures interpretation

1 sandstone, with solitary bioclasts trough cross-bedding tidal channel fills 2 sandstone, bioclast-rich massive or crude cross-bedding, final fill of tidal channels bioturbations, 3 sandstone, well sorted trough or tabular cross-bedding tidal bars 4 sandstone, well sorted low angle cross-bedding to beach deposits horizontal bedding 5 sandstone, coarse-grained; megaripples, shell beds tempestites conglomerate, poorly sorted 6 sandstone, fine-grained; siltstone ripple cross-bedding to tidal flat deposits laminated, flaser and lenticular bedding 7 micritic carbonate peloidal, cracks calcre tes 8 sandstone, fine-grained; ripple cross-bedding, horizontal fluvial channel fills, floodplain minor silt- and claystone bedding, massive and lake deposits 9 calcareous oolite cross-bedding, massive, or ooid bars bioturbated 10 limestone in situ corals and molluscs coral-oyster biostromes

Cretaceous age is generally accepted. Biostrati- nated by juveniles of the bivalves Meleagrinella graphy of the marine units depends heavily on radiata (Pl. 2: 5), Liostrea dubiensis, Nanogyra ammonites and bivalves, but age assignments are nana and Eomiodon cutleri, as well as the gastro- not consistent (see Aitken 1961). Preliminary pods Pseudomelania dietrichi, Cryptaulax sp. and biostratigraphic interpretations of our samples Promathildia sp.. Rare elements include serpulid support the following dates: Oxfordian? to Late worm tubes, crustaceans (two species of ostra- Kimmeridgian for the Nerinea Bed (based on the cods, including Pirileberis; decapod crab), ostracod Majungaella oxfordiana, Bate (1975) and benthic foraminifera and fragments of echinoids ammonites (G. Schweigert, pers. comm., 2002 and and crinoids. Of the highly inequivalved M. ra- Heinrich et al. 2001)); early Tithonian for the Tri- diata, right valves were twice as common as left gonia smeei Bed (based on ammonites (G. Schwei- valves. Both taxonomic composition and relative gert, pers. comm., 2001) and charophytes (M. abundance hardly vary between samples, and Schudack, pers. comm., 2002)); and Early Cretac- 6.7% of the bivalves were still articulated. eous, possibly Valanginian to Hauterivian, for the Trigonia schwarzi Bed (based on palynomorphs Vertebrates (Heinrich et al. 2001)). Comparatively few vertebrate remains are known from the Lower Saurian Bed, and all are disarticulated. Sample Tin Oa yielded a single Sedimentological and palaeontological analysis vertebra of an indeterminate teleost fish as well as poorly preserved scales and bones of fishes Lower Saurian Bed that do not permit taxonomic determination (Arratia et al. 2002). Other aquatic or semi-aqua- Facies tic vertebrates have not yet been recovered. The The Lower Saurian Bed consists predominantly only terrestrial vertebrates known to date were of ripple cross-bedded, fine-grained sandstones reported by the GTE (Janensch 1961, see Ta- and siltstones interbedded with massive clay-rich ble 2). The material includes the distal end of a siltst ones. large femur and a small manus claw of the saur- opod Brachiosaurus brancai. The femur repre- Invertebrates sents an adult, the small claw is apparently from Macrobenthic molluscs are remarkably rare a juvenile individual. Several isolated teeth as- (samples Tin 1, Tin Oa), but mesobenthic signed to the theropod ‘Megalosaurus ingens’ (<5 mm) elements are abundant in more than and some theropod teeth that might belong to twenty samples from horizon Tin Oa. They con- ‘Ceratosaurus roechlingi’ and ‘Allosuurus tenda- stitute a moderately diverse assemblage domi- gurensis’ were also found (Janensch 1925b). Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 25

Flora existence of water bodies is indicated by fish re- A few samples from the Lower Saurian Bed mains. It is possible that the terrestrial verte- (Tin 1, Tin Oa) yielded an impoverished palyno- brate assemblage achieved similar levels of di- flora. The dominant element are pollen grains of versity as that from the Middle and Upper the conifer family Cheirolepidiaceae (ClassopoZ- Saurian Beds, but this idea cannot be tested be- Zis) associated with pollen from other conifers cause of the small size of the sample, and possi- (bisaccate pollen, Araucariacites), possible repre- ble collection bias. sentatives of the Podocarpaceae and Araucaria- ceae, and a few pteridopyhtic spores. No marine palynofossils were observed. Nerineu Bed Similarly, the mesoflora is dominated by cuti- cles of cheirolepidiaceans (Tin Ob; P1. 1: 6), while Facies cuticles of the Araucariaceae and ginkgos are The base of the Nerinea Bed consists of trough less common. cross-bedded or massive, poorly sorted, medium- to coarse-grained sandstones. The sandstones Environmental interpretation form fining-upward sequences and show highly The sediments of the Lower Saurian Bed suggest variable to bipolar transport directions. They are variable water energies of low to moderately occasionally overlain by massive to indistinctly high intensity. The marked asymmetry in valve cross-bedded fine- to medium-grained sandstones sorting of shells points to selective transport by that sometimes contain a diverse assemblage of currents and/or waves. However, the unvariable invertebrates. Stacked sequences of mainly faunal composition and frequency distributions trough cross-bedded, medium- to fine-grained of samples and the occurrence of articulated sandstones with unimodal transport directions shells render large-scale transport and faunal are also common. Further lithofacies types com- mixing unlikely. Consistent with the general set- prise well sorted, horizontally to low-angle cross- ting of the Tendaguru Beds (see below), the se- bedded sandstones and isolated swaley cross- diments and invertebrate assemblages of the bedded sandstones (Pl. 1: 1). Lower Saurian Bed are tentatively assigned to a tidal flat environment. The invertebrate fauna Invertebrates clearly demonstrates a marine influence. How- The bivalve taxa from the Lower Saurian Bed ever, the dominance of generally eurytopic bi- also occur scattered through several sandstone valves and gastropods, relatively low diversities layers at the base of the Nerinea Bed (e.g., Tin 2, and the extreme abundance of juvenile inverte- Tin 3/base, Tin 3b), where they reach maximum brates suggest a certain degree of environmental sizes that are distinctly larger. Additional com- stress. This may have its origin in a combination mon elements are the bivalves Protocardia of salinity fluctuations and relatively long subaer- schencki, Grammatodon irritans and various spe- ial exposure times that shorten the time avail- cies of limids and pectinids, whereas gastropods able for suspension-feeding. are rare. Also rare are nektic elements including With respect to the few vertebrate remains, ammonoids, nautiloids and belemnites. The cal- adult brachiosaurs are generally regarded as careous microfauna in these samples is represen- high-browsing herbivores (e.g., Paul 1988, McIn- ted by a moderately diverse ostracode assembla- tosh 1997), whereas small juvenile and medium- ge, including MajungaelZa oxfordiana (Pl. 2: 8) sized subadult individuals of Brachiosaurus bran- and Cytherella umbilica (Pl. 2: 12) and benthic cai must have fed closer to the ground. Like foraminifera. The most fossiliferous sample (Tin other sauropods, B. brancai was essentially ter- 3d) stems from calcareous concretions within a restrial (McIntosh 1997). The admittedly poor bioturbated, fine-grained sandstone. It is domina- fossil record of terrestrial vertebrates suggests a ted by epifaunal and infaunal, suspension-fee- vegetated environment in the hinterland of Ten- ding bivalves that are fairly evenly distributed in daguru with habitats where juvenile and adult terms of their relative abundances (Fig. 3). The brachiosaurs could gather food from high- and lefthight valve ratio of the most common taxa is low-growing plants, of which so far conifers, close to one and double-valved individuals occur. ginkgos and pteridophytes can be demonstrated. The levels of fragmentation, abrasion, encrustati- The region was also inhabited by large preda- on and bioerosion are low. This layer also yiel- tors/scavangers such as Megalosaurus ingens. The ded six species of ostracods, including Cytherella 26 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 27

Fig. 3. Faunal composition and relative abundance of macroinvertebrates in sample Tin 3d. Scale bar equals 1 cm. NI"~:num- ber of individuals; NSp:number of species. sp. and Majungaella cf. oxfordiana, as well as be- Flora nthic foraminifera. Palynofloras are again dominated by conifer pol- len (mainly Classopollis, Vertebrates but also Araucariacites). Low diversity or monospecific assemblages of di- According to Janensch (1914b) and (Hennig noflagellates occur in samples Tin 2 and Tin 4d 1914a), the marine sandstone units separating and somewhat more diversified assemblages with the three dinosaur-bearing units yielded only in- Barbatacysta, Gonyaulacysta group and chorate significant fragments of dinosaur bones. Well- cysts were found in samples Tin 3b and Tin 3d. preserved vertebrate remains from the Nerinea Sample Tin 4d yielded psilate ?dinoflagellates. Bed are still to be discovered.

4 Colour-Plate 1. 1. Low-angle cross-bedded beach sandstones in the Nerineu Bed Tingutinguti stream section. 2. Calcrete horizon in the Middle Saurian Bed Tingutinguti stream section. 3. Trough cross-bedded tidal channel sandstones in the Trigo- niu smeei Bed; Dwanika stream section. 4. Heterogenous intertidal sediments in the Trigoniu smeei Bed; Tingutinguti stream section. 5. Conglomerate horizon in the Trigonia smeei Bed; small tributary of the Bolachikombe stream. 6. Cheirolepidiocutis sp. (cuticule of a cheirolepidiacean conifer); Lower Saurian Bed, sample Tin Ob, x 57; MB.Pb.200211045. 7. Barbatacysta cre- berburbutu (Erkmen & Sarjeant) Courtinat (marine dinoflagellate); Trigoniu smeei Bed, size 36 pm; IY27. 8. Densoisporites velatus Weyland & Krieger (pteridophwc spore); Middle Saurian Bed, size 52 pm; IY15. 9. Cullialusporites trilobutus (Balme) Sukh Dev (conifer pollen with affinity to Araucariaceae); Middle Saurian Bed, size 60 pm; IY31. 28 Aberhan, M. et al., Palaeoecologv of the Tendaguru Beds Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 29

The mesoflora is rather rare but seems to be all, the Nerinea Bed appears to represent very diverse. In sample Tin 3d Cheirolepidiaceae, Po- shallow subtidal to lower intertidal environments docarpaceae, Ginkgoales and Cycadales are that were strongly influenced by tides and, at found as cuticules. A new conifer genus is pre- least intermittently, by storms. served as fusain.

Environmental interpretation Middle Saurian Bed Trough cross-bedded sandstones with evidence of bipolar and variable transport directions were Facies most likely deposited in tidal channels. The highly The basal part of the Middle Saurian Bed is fossiliferous invertebrate sample from bioturbated composed of fining-upward sequences that con- sandstone (Tin 3d) probably represents the final sist of ripple cross-bedded, fine-grained sandsto- fill of such a tidal channel. In this sample, the ba- nes and siltstones, and massive silt- and claysto- lanced proportion of epifauna to infauna suggests nes. These sediments are cut by lenses consisting a stable, but still relatively soft substrate. The ta- of ripple cross-bedded sandstones. In the upper phonomic data indicate that post-mortem trans- part, several peloidal limestone horizons are in- port was insignificant and that the residence time tercalated within the main sequence (Pl. 1: 2). of shells on the sediment surface was short. Faunal Limestone intraclasts are also present in adjacent composition, the maximum size of taxa and diver- sandstone beds. sity values testify to normal marine conditions. The moderately diverse assemblages of dinoflagellates, Invertebrates ostracods and benthic foraminifers in the same Several samples from the base of the Middle sample support this view. It must be kept in mind, Saurian Bed (Tin 6, Tin 7b) yielded a macroben- however, that this sample is not representative for thic mollusc assemblage characterised by low the Nerinea Bed as a whole. In particular, higher species richness and high dominance. Represen- parts of this unit are unfossiliferous or poorly fossi- ting nearly 80% of the total number of speci- liferous with relatively low diversity. Sample Tin mens, the shallow burrowing neomiodontid bival- 4d, for example, only yielded questionable psilate ve Eomiodon cutleri (= Cyrena sp. of Dietrich dinoflagellates suggesting some form of environ- 1933; e.g., PI. 2: 2) strongly dominates. Indivi- mental stress, possibly fluctuating salinities. The duals of this species exhibit a broad size spec- absence or scarcity of skeletal hardparts is not ne- trum, high degree of articulation and low degree cessarily the result of a primary absence of shell- of fragmentation. Two species of gastropds, Pro- bearing invertebrates, but may be due to shell dis- mathildia sp. and Pseudomelania dietrichi (PI. 2: solution during early diagenesis. Nothing is known 4), and a mytilid bivalve are far less common so far about the marine vertebrate fauna of the (Fig.4). Stenohaline groups such as corals and Nerinea Bed and its coeval terrestrial counterparts. echinoderms appear to be absent. The mesoben- Sandstones with unimodal transport directions thos is dominated by juveniles of Promathildia. are interpreted as subtidal sand bars. Horizon- Ostracods are common, moderately diverse and tally to low-angle cross-bedded sandstones are include the genus Darwinula (Pl. 2: 9). most likely to represent beach deposits (Pl. 1: 1), In the remainder of the Middle Saurian Bed whereas swaley cross-bedded sandstones prob- macro- and microinvertebrates only occur spora- ably formed as storm layers (tempestites). Over- dically. Rare ostracods from samples Tin 7d and

4 Plate 2. 1. Fulcimytilus dietrichi Cox (bivalve), left valve view; Upper Saurian Bed, GTE site I; MB.M.1566. 2. Eomiodon (Africomiodon) cutleri Cox (bivalve), right valve view; Upper Saurian Bed, GTE site G; MB.M.1645.1. 3. Zndotrigonia ex gr. smeei (J. de C. Sowerby) (bivalve), right valve view; Trigoniu smeei Bed, sample Mai 5Bed 1; MB.M.1708. 4. Pseudomelania dietrichi Cox (gastropod); Middle Saurian Bed, GTE site p; MB.Ga.ll20.1. 5. Meleagrinella rudiatu (Trautschold) (bivalve), left valve view; Nerinea Bed, sample Tin 3d; MB.M.1711.1. 6. Meundrophyllia oolifotithonica (Dietrich) (coral); Trigonia smeei Bed, sample Kor 24; MB.K.1594. 7. Bernissartia sp. (tooth of a dwarf crocodile); Middle Saurian Bed (bone bed Wj), GTE site dy; MB.R.3259; a, lingual view; b, ?anterior view. 8. Majunguella oxfordiuna Bate (ostracod); external view of male left valve; Nerinea Bed, sample Tin 2a. 9. Dunvinulu sp. (ostracod); internal view of right valve; Middle Saurian Bed, sample Tin 7b. 10. Hybodus sp. (tooth of selachian fish); labial view; Upper Saurian Bed, sample Dwa 5a; MB.f.7732. 11. Sphenodus sp. (tooth of a selachian fish); labial view; Upper Saurian Bed, GTE site Om; MB.f.7729. 12. Cytherellu cf. umbilica Bate (ostra- cod); external view of right valve; Nerineu Bed, sample Tin 2a. 13. Glyptostroboxylon n. sp. (conifer); Trigoniu smeei Bed, sample Tin 9h; MB.Pb.2002/1044; scale bar equals 100 pm. 30 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds

Tin 7g contain Cypridea sp., and sample Tin 7i fish remains (Heinrich et al. 2001). Teeth of a yielded Darwinula sp. Bivalves and gastropods selachian, scales and teeth of Lepidotes sp., as (samples Tin 7c, f, i, k, 1) include the above-men- well as a scale of a pholidophorid-like fish and tioned taxa as well as small individuals of the vertebrae of an indeterminate teleost have been eurytopic oysters Liostrea and Nanogyra. identified (Arratia et al. 2002). A selachian spine collected from the Middle Saurian Bed exposed Vertebrates at site Bo was previously reported by Hennig The Middle Saurian Bed, as exposed in the Ting- (1914b). utinguti stream section, produced only a few, The dinosaurs recovered by the GTE are the small fragments of bones and teeth of dinosaurs hallmark of the Middle Saurian Bed (Table2). that do not show any diagnostic features, and The following sauropods have been identified:

Table 2 Stratigraphic distribution of vertebrate taxa of the Tendaguru Beds. Note that the Transitional Beds of previous workers are here included in the corresponding Saurian beds. The sandstone units separating the three dinosaur-bearing units yielded no or only insignificant fragments of vertebrate remains, which are referred to in the text. (+) denotes that stratigraphic position is uncertain; ? denotes that taxonomic assignment is uncertain.

Taxa Lower Middle Upper Saurian Bed Saurian Bed Saurian Bed Elasmobranchii Hybodus sp. + Hybodontidae indet + Lonchidion sp. nov. + Sphenodus sp. + Indet. Selachian + Engaibatis schultzei Arratia et al., 2002 Actinopterygii Lepidotes tendaguruensis Arratia & Schultze, 1999 + Lepidotes sp. + c ‘Pholidophorid’ + Indet. teleost + Indet. fishes + c + Amphibia Lissamphibia (Salientia?). + Reptilia Sphenodontidae indet. + Paramacellodidae indet. + Bernissam’a sp. + + Crocodylia indet. + + Tendaguripterus recki Unwin & Heinrich, 1999 + Dsungaripteroidea indet. + ‘Rhamphorhynchoidea’ indet. + Elaphrosaurus bambergi Janensch, 1920 + Coelurosauria indet. + ‘Allosaurus tendagurensis’ Janensch, 1925 9 ‘Ceratosaurus roechiingi’ Janensch, 1925 ? ‘Labrosaurus stechowi’ Janensch, 1920 ‘Megalosaumingens’ Janensch, 1920 + Theropoda indet. Barosaurus africanus (Fraas, 1908) Barosaurus gracilis Janensch, 1961 + Dicraeosaurus hansemanni Janensch, 1914c + Dicraeosaurus sattleri Janensch, 1914c + Brachiosaurus brancai Janensch, 1914c + + Janenschia robusta (Fraas, 1908) + Tendaguria tanzaniensis Bonaparte et al., 2000 (+) Sauropoda indet. + + Kentrosaurus aethiopicus Hennig, 1915 + + Dryosaurus Zettowvorbecki (Vuchow, 1919) + Dinosauria indet + Mammalia Staflia aenigmafica Heinrich, 1999 + Tendagurodon janenschi Heinrich, 1998 + Brancatherulum tendagurense Dietrich, 1927 + Tendagurutheriurn dietrichi Heinrich, 1998 + Mammalia indet. + + Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 31

Brachiosaurus brancai, Dicraeosaurus hanseman- sphenodontid lepidosaurs, squamates (Parama- ni and Barosaurus gracilis (Janensch 1914c, cellodidae indet.: Broschinski 1999) and croco- 1961). They are associated with theropods, diles (e.g., Bernissartia: Heinrich et al. 2001; see among them Elaphrosaurus bambergi, ‘Megalo- also Janensch 1914b; P1. 2: 7). Pterosaurs (Ten- saurus ingens’, ‘Labrosaurus stechowi’ and ‘Allo- daguripterus recki: Unwin & Heinrich 1999) and saurus tendagurensis’ (Janensch 1925b). In addi- mammals have also been recovered, the latter tion, two ornithischians are reported (Hennig represented by a jaw fragment of an eupan- 1925, Janensch 1955), Kentrosaurus aethiopicus tothere (Tendagurutherium dietrichi), a tooth of and Dryosaurus lettowvorbecki. a triconodont (Tendagurodon janenschi) and The transitional sands between the Middle cheek teeth of a haramiyid (Stafia aenigmatica) Saurian Bed and the Trigonia smeei Bed, here (Heinrich 1998, 1999b, 2001; Table 2). included in the Middle Saurian Bed, contain ske- letal remains of Barosaurus gracilis, Dicraeo- Flora saurus sp., Brachiosaurus brancai and Kentro- Again, pollen grains derived from a conifer-do- saurus aethiopicus (Hennig 1925, Janensch 1961). minated terrestrial vegetation are the most abun- These assemblages are dominated by disarticu- dant palynomorphs in the Middle Saurian Bed lated limb bones, many of which are water-worn. (e.g., P1. 1: 9). Dinoflagellates are rare and inclu- Site Aa produced a fragmentary humerus of B. de short-spined forms (Tin 6) and psilate forms brancai overgrown by oysters (Janensch, GTE (Tin 7b). Freshwater algae (Zygnemataceae: field book, p. 140). Site p, immediately overlying Ovoidites, see Schrank 1999) occur in Tin 6 and the Nerinea Bed, yielded a string of nearly ar- Tin 7f In sample Tin 7d two specimens of fairly ticulated caudal vertebrae of the same species well-preserved charophytes were found. that were associated with marine invertebrates With respect to cuticles, Tin 7f constitutes the including the bivalve Eomiodon, gastropods and most productive sample within the Tendaguru stalk fragments of crinoid stems (Hennig 1914a; Beds, yielding a nearly monotypic assemblage of Janensch, GTE field book, p. 56). Cheirolepidiaceae and a few specimens repre- Based on field sketches of the GTE, Heinrich senting Podocarpaceae. (1999a) distinguished four main preservational states of dinosaurs from the Middle Saurian Bed Environmental interpretation (1) fairly complete skeletons (e.g., Brachiosaurus The majority of fine-grained sediments from the brancai, site S; Dicraeosaurus hansemanni, site basal part of the Middle Saurian Bed were depo- m); (2) partial skeletons (e.g., Dryosaurus lettow- sited on siliciclastic tidal flats of a lagoonal sy- vorbecki, site dy); (3) bone fields consisting stem, whereas the sandstone lenses represent mainly of disarticulated bones (e.g., Kentrosaurus small tidal channels. The taphonomic data from aethiopicus, site St); and (4) solitary bones and macrobenthic assemblages in this part of the sec- teeth (most taxa and sites). Multi-taxon assem- tion indicate the absence of large-scale lateral blages (e.g., site Q: B. brancai, D. hansemanni, transport and sorting of valves by currents. By K. aethiopicus) and single-taxon bone assem- analogy with modern ecosystems, low diversity, blages (e.g., site S: B. brancai, site m: D. hanse- high abundance and large populations hint at an manni) have been recognized. In the latter cate- elevated degree of environmental stress. Eomio- gory, single-individual assemblages (e.g., D. don has long been recognised as an eurytopic hansemanni, site m) and multi-individual assem- bivalve, capable of tolerating reduced salinities blages (e.g., B. brancai, sites S, XX) can be dis- (e.g., Huckriede 1967, Hallam 1976, Fiirsich tinguished. The bone assemblages of B. brancai 1994). This, in combination with the lack of ste- are dominated by adult and old adult individuals nohaline groups and the marginal marine setting (Heinrich 1999a). By contrast to the sauropods of the Tendaguru Beds, is indicative of low-ener- and ornithischians, the theropod dinosaurs are gy, brackish water environments, an interpretati- mainly represented by isolated teeth and bones, on that is supported by the presence of the except for the incomplete skeleton of Elaphro- ostracod Darwinula and of rare short-spined and saurus bambergi recovered from site dd (Ja- psilate dinoflagellates in the same samples. Both nensch 1925b). the dinoflagellates (e.g., Schrank & Mahmoud Acid preparation of matrix recovered from 1998) and the ostracod (van Morkhoven 1963, two bone beds (Jg, Wj) at site dy by the GTE Neale 1988) provide evidence for the influence yielded skeletal remains of small, land-dwelling of fresh to slightly oligohaline waters. The abun- vertebrates including lissamphibians (Salientia?), dance of juveniles of Promathildia sp. suggests 32 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds

that this species lived close to the limits of its ble-peaked size distribution pattern for the fe- environmental tolerance. Periodically, fluctuating mur of D. lettowvorbecki collected at site dy salinity values probably caused high juvenile resulted from a year-to-year input of bones mortality. According to Dietrich (1933) shell (Heinrich 1999a), rather than as a result of mass beds dominated by Cyrena sp. (= Eomiodon) death events caused by a single period of and indicative of weakly brackish water conditi- drought. Subsequent reworking may have con- ons occur repeatedly in the Jurassic part of the centrated bones in lag deposits of tidal channels. Tendaguru Beds. The bone accumulations in the transitional sands The presence of the nonmarine ostracod genus below the Trigonia smeei Bed, dominated by Cypridea (see Neale 1988) together with well- abraded sauropod limb bones, are possibly due preserved charophytes and other freshwater al- to wave and/or current action that resulted in gae, indicates the strong influence of freshwater the abrasion, destruction, transportation and in Tin 6, Tin 7d, Tin 7f and Tin 7g. Ostracods sorting of skeletal elements (Janensch 1914b). from the Middle Saurian Bed and of partly mar- The associated invertebrates show that marine ine and partly freshwater affinities, as well as waters influenced the depositional environment. charophytes suggesting environments with partly Among land-dwelling vertebrates the domi- brackish, partly freshwater influences were also nant group were large herbivorous dinosaurs. reported by Schudack (1999) and Schudack & The largest species were quadrupedal sauropods, Schudack (2002). among them Brachiosaurus brancai which is gen- Peloidal limestones in the upper part of the erally assumed to have been able to reach up to Middle Saurian Bed are interpreted as pedo- 13 m to feed on tree foilage (e.g., Paul 1988, genic calcretes (PI. 1: 2). Their presence indi- Christiansen 1995, McIntosh 1997, Christian & cates periods of subaerial exposure and the on- Heinrich 1998). It was followed by the high- set of soil formation. Calcrete intraclasts within browsing Barosaurus gracilis and the relatively adjacent sandstone beds testify to erosive re- short-necked Dicraeosaurus hansemanni, which working of calcrete horizons. The highly sporadic probably fed at a lower level. By contrast, the occurrence, in this part of the section, of mol- foraging ranges of the low level-feeding or- luscs typical of marginal marine habitats indi- nithischians Kentrosaurus aethiopicus and Dryo- cates only a very weak marine influence. We in- saurus lettowvorbecki were possibly restricted to terpret the corresponding environments as heights of no more than two meters above the sabkha-like coastal plains with brackish lakes ground. As at other dinosaur sites (Currie 1997), and ponds. the flesh-eating theropods were outnumbered by With regard to the land-dwelling vertebrate as- herbivorous sauropods, even though the precise semblage a crucial issue is the degree to which number of individuals, especially for the thero- post-mortem transportation of dinosaur remains pods, has still to be calculated. The pterosaur may have taken place. The broad spectrum of Tendaguripterus recki possibly fed on hard- disarticulation stages and the water-worn nature shelled invertebrates such as bivalves (D. Unwin, of many bones indicate carcass decay and a cer- pers. corn., 2002), and is likely to have inhab- tain amount of post-mortem transport prior to ited the coasts of a shallow sea and margins of burial (Heinrich 1999a). Mass accumulations of rivers. mainly disarticulated bones of the herbivorous The taxonomic diversity of the herbivorous di- dinosaurs Kentrosaurus aethiopicus (site St) and nosaurs and their estimated foraging heights sug- Dryosaurus iettowvorbecki (site dy) were origin- gest a diverse vegetation in the hinterland, with ally thought to represent a sudden mass death numerous habitats and niches that also offered event due to drowning (Janensch 1914a, c; Hen- adequate living conditions for lissamphibians nig 1925). More recently, Russell et al. (1980: (Salientia?), terrestrial sphenodontid lepidosaurs, 172) speculated that these mass accumulations squamates and mammals. The triconodontid “may be interpreted as the result of a concentra- mammal Tendagurodon janenschi was most tion of low-browsing herbivores in a restricted likely terrestrial and probably insectivorous or area of relatively plentiful, low-growing vegeta- partly carnivorous, but the exact diet is un- tion during a period of drought. Overpopulation known. The shrew-sized eupantothere Tendagur- led to overexploitation and an abundance of ske- utherium dietrichi possessed shearing teeth letal litter which was swept into concentrations (Heinrich 1998). It lived on land and possibly by flowing water after the return of normal plu- fed on insects and other small invertebrates. The viosity”. Our observations suggest that the dou- haramiyid Stafia aenigmatica was a small terres- Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 33

Fig. 4. Faunal composition and relative abundance of macroinvertebrates in sample Tin 7b. Scale bar equals 1 cm. For key of abbreviations see Fig. 3. trial allotherian mammal. Its dentition suggests Invertebrates that it processed soft food items such as plant A prominent feature of the macroinvertebrate material, as previously suggested for other hara- fauna is the occasional concentration of bivalves miyid taxa (Butler & McIntyre 1994). The pre- in shell beds. Most conspicuous are mono- to sence of crocodiles indicates freshwater to littor- paucispecific skeletal concentrations dominated al environments and adjacent terrestrial areas. by large and thick-shelled individuals of shallow infaunal trigoniid (Pl. 2: 3) and astartid bivalves (e.g., Tin 9m, Mai 5, Mai 7, Dwa 01; see also Trigonia smeei Bed Dietrich 1933). The valves are almost invariably disarticulated, but not fragmented, preferentially Facies orientated in a convex-up position and typically The Trigonia smeei Bed, like the Nerinea Bed, lack signs of encrustation and bioerosion. Som- starts with trough cross-bedded or massive, poor- ewhat more diverse fossil assemblages (e.g., Tin ly sorted medium- to coarse-grained sandstones 9g, Tin 9k), which in addition to trigoniids may that show highly variable transport directions contain oysters and other bivalves, gastropods, (Pl. 1: 3). They are overlain by small-scale cross- serpulids and corals, are regarded as a variation bedded or ripple cross-bedded sandstones and of this type of shell bed. by minor silt- and claystones with flaser or lenti- A second type of skeletal concentration is asso- cular bedding that includes small sandstone len- ciated with fine-grained, horizontally to low-angle ses (Pl. 1: 4). The fine-grained sediments are re- cross-bedded sandstones (e.g., Tin 9i, Kor 10, 12), peatedly dissected by poorly sorted, where the lamination reflects subtle changes in conglomeratic sandstone horizons with mud grain size. Thin shell pavements of small, single- clasts, reworked concretions, megaripple surfaces valved bivalves occur preferentially in the slightly and/or skeletal concentrations of thick-shelled bi- coarser grained laminae. Dominant taxa include valves (see below; P1. 1: 5). The troughs of mega- Meleagrinella, small oysters, Protocardia, Entolium ripple surfaces are commonly filled with fine- and Limea. The preferred orientation of valves in grained sediment. Medium- to coarse-grained, such pavements is either convex-up or convex- trough cross-bedded sandstones dominate the down. Between pavements, the same assemblage upper part of the Trigonia srneei Bed. Northeast may occur scattered within the sediment. and southwest of Tendaguru, the sandstones in- A mixed siliciclastic-oolitic horizon approxi- terfinger with oolitic limestones. mately 8 km northwest of Tendaguru (Kor 24, 34 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds

Fig. 5. Faunal composition and relative abundance of macroinvertebrates in sample Kor 24. Scale bars equal 1 cm. For key of abbreviations see Fig. 3.

Fig. 1) is characterised by concentrations of colo- (Arratia et al. 2002), no other vertebrate materi- nial corals (e.g., P1. 2: 6) that are up to 20 cm in al was found during field work by the German diameter and largely occur in life position. Also and German-Tanzanian Tendaguru expeditions. common are large, thick-shelled cementing oy- sters (Fig. 5). Corals and thick-shelled oysters Flora served as hard substrates for small cementing oy- sters and provided an ideal substrate for the bor- The majority of palynologically useful samples ing bivalve Lithophaga. The latter, along with from the Tendaguru succession are from this unit crowded juveniles of cementing oysters, domi- (Tin 9f to Tin 9r). All samples contain marine nate the assemblage in terms of relative abun- dinoflagellates (e.g., P1. 1: 7) occasionally inclu- dance but, compared to corals, contributed little ding chorate forms. Other organic-walled micro- to the estimated biovolume of the assemblage. fossils of marine origin include “chitinous” mi- The level of fragmentation of corals and mol- croforaminifera (organic linings of tests of small luscs is remarkably low. foraminifera in Tin 9f and Tin 9h/2) and acri- The calcareous microfauna of the Trigonia tarchs (Micrhystridiurn in Tin 91). In addition, the smeei Bed is represented by moderately diverse freshwater alga Ovoidites occurs in Tin 91, and assemblages of ostracods and benthic foramini- Tin 9p/5 yielded moderately well-preserved speci- fera (samples Kin 2a, Tin 9j, Tin 9p/3, Tin 9/p5, mens of the charophyte genus Clavator. Tin 9qb, Tin 9r). Among ostracod genera identi- The mesoflora also reaches its highest diver- fied so far Majungaella is common. The preser- sity within this section and is particularly concen- vational state of the calcareous microfauna, trated in samples Tin 9h, 9j, 9p and 9q. Apart mainly due to weathering and/or recrystalliza- from three types of Cheirolepidiaceae, cuticles of tion, is poor to moderate. Cycadales and pteridosperms of Dicroidium- or Pachypteris-type are present. Abundant fusain represents three types of podocarpacean wood, Vertebrates two species of Glyptostroboxylon (e.g., P1. 2: 13), With the exception of a fragmentary vertebra of one species of Platyspiroxylon and an as yet un- an indeterminate teleost fish in sample Tin 9n/o described araucarian wood. Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) ~~ 35

Environmental interpretation associated with mixed siliciclastic-oolitic sedi- ments, as demonstrated by the massive growth The coarse-grained sandstones with highly varia- forms of corals, high percentage of cementing ble transport directions are interpreted as large elements and extraordinarily thick shells of oy- tidal channel deposits (Pl. 1: 3). Grain-size, lar- sters, other bivalves and some gastropods. The ge-scale sedimentary structures and lack of trace marked dominance of epifauna and presence of fossils indicate a high-energy regime and fre- cementing oysters and serpulids within the sedi- quent reworking. This resulted in a highly mo- ment points to a firm and stable substrate. Sedi- bile substrate, which probably was responsible mentation rates seem to have been low, as indi- for the complete absence of epifaunal and infau- cated by the relatively high degree of bioerosion nal elements. and encrustation. Corals and oysters did not The overlying cross-bedded sandstones and form a distinct relief on the sea floor, but only minor silt- and claystones with flaser or lenticu- low thickets. All in all, the sample is characteris- lar bedding represent tidal flat deposits and asso- tic of an autochthonous coral-oyster biostrome ciated tidal channel fills (Pl. 1: 4). Pavements of that colonized a stable substrate within a wave- small, single-valved bivalves in horizontally to and/or current-influenced, normal marine and low-angle cross-bedded, fine-grained sandstones shallow water environment. were formed, apparently, by tidal currents in A predominantly marine environment of the small flood and ebb tidal deltas and along the Trigonia smeei Bed is also evident from calcar- beach. eous microfossils and from palynological data, as The taphonomic signatures of shell concentra- indicated by the abundant marine ostracods, tions in coarse-grained sediments suggest episo- benthic foraminifera, dinoflagellates and, less dic exhumation of infaunal individuals and rela- commonly, by organic-walled microforaminifera tively rapid redeposition as is typical of high- and acritarchs, which are usually interpreted as energy events such as storms (see also Dietrich indicative of shallow marine environments (e.g., 1933). The erosive base of shell beds is also con- Sarjeant and Taylor 1999). On the other hand, sistent with a storm-induced origin. The lack of the abundance of Clussopotlis and a diverse me- articulated bivalves can be explained by the re- soflora suggests proximity to a vegetated hinter- working of dead individuals only. Size sorting land dominated by members of the xerophytic and the hydrodynamically stable convex-up posi- conifer family Cheirolepidiaceae and acting as a tion of most shells point to post-mortem trans- source of plant material. For a single sample port of shells and the presence of currents at the (Tin 9p/5), the charophyte genus Cluvutor indi- time of deposition. Long distance transport, how- cates freshwater influence (M. Schudack, pers. ever, is not likely to have occurred, as indicated comm.). by taphonomic features such as the low degree of fragmentation. Storm beds have their highest preservation potential between fair weather wave base and storm wave base. Sedimentologi- Upper Saurian Bed cal evidence indicates that the various sediments of the Trigoniu smeei Bed were deposited above Facies fair weather wave base. In such shallow marine The basal part of the Upper Saurian Bed con- environments it is not surprising that original sists of small-scale cross-bedded and ripple cross- concentrations of hard parts by storm processes bedded, fine-grained sandstones and siltstones subsequently were modified by currents. The with intercalations of isolated micritic dolomite coarse-grained, poorly sorted horizons lacking layers. These sediments are overlain by ripple shell beds and overlain by fine-grained sediment cross-bedded and small-scale cross-bedded, fine- apparently represent couplets typical of tempes- grained sandstones and by claystones. tites. The upper part of the Trigoniu smeei Bed Invertebrates again represents tidal channel and sand bar de- With few exceptions, the Upper Saurian Bed is posits. The oolitic limestones with which they in- devoid of macroinvertebrates. A low diversity as- terfinger resemble modem ooid sands and ob- semblage, very rich in articulated shells of Eo- viously formed as high-energy ooid shoals. rniodon cutleri (e.g., P1. 2: 2), occurs in the lower Adaptation to relatively high turbulence levels part of the Upper Saurian Bed at Kitukituki (Tin can also be seen in the coral-oyster bed that is Sol), and a monospecific assemblage of abun- Aberhan, M. et al., Palaeoecology of the Tendaguru Beds 36 ~ dant articulated juveniles of E. cutleri was sam- (e.g., site P: Janenschia robusta), as well as sin- pled from the base of the unit at Dwanika (Dwa gle-taxon assemblages (e.g., site 0: Dicrueo- A). A few meters up-section (Dwa 5a, 5b) rare saurus sattleri; site k: Barosaurus africanus) and juveniles of Meleagrinella, Eomiodon and gastro- multi-taxon assemblages (e.g., site ab: B. brancai ?, pods occur, and a single valve of Falcimytilus die- D. sattleri, B. africanus, Sauropoda indet.) have trichi (Pl. 2: 1) was found in sample Dwa 6b/l. been documented by the GTE (Heinrich 1999a). Samples Dwa 5b, 6c and 7b yielded a few poorly Most of the sauropod bone assemblages appear preserved ostracods, of which only one taxon, to represent single-individual assemblages. The Cypridea sp., could be more precisely identified Barosaurus africanus bone assemblages recov- from Dwa 5b. ered from the Upper Saurian Bed are dominated by adult and old adult individuals (Heinrich Vertebrates 1999a). Of special interest are vertically or- The most common fish remains from the Upper iented, articulated fore feet of Janenschia robusta Saurian Bed are isolated scales and teeth of Le- (site 5) and Brachiosaurus brancai (site R) as pidotes tendaguruensis (Arratia et al. 2002). Sev- well as articulated hind feet of Barosaurus ufrica- eral fairly complete specimens of this taxon were nus from sites XI11 and 28 (Janensch 1914~ described by Arratia & Schultze (1999), and a 1961). mass accumulation of L. tendaguruensis reported Isolated teeth of crocodiles were also found at from site M (Hennig 1914b, Arratia & Schultze site 2 (Janensch, unpublished). Many pterosaur 1999) merits special mention. Selachians (Sphe- bones, originally described by Reck (1931), were nodus sp.; e.g., P1. 2: ll), a pycnodontid and based on non-diagnostic elements and have re- other unidentified fish remains were previously cently been identified as indeterminate dsungar- recognized by Hennig (1914b). Additional col- ipteroids (Unwin & Heinrich 1999). Noteworthy lecting in the Dwanika stream section (Dwa 5a) is a mass accumulation of postcranial pterosaur yielded several selachian taxa previously un- bones reported from site MD (Reck 1931). known from the Tendaguru Beds, including three The poorly preserved dentary of Brancatheru- hybodonts (Hybodus sp., Hybodontidae indet., lum tendagurense (Dietrich 1927) from site IV Lonchidion sp.; see also P1. 2: 10) and the new documents the presence of eupantotherian mam- neoselachian batoid Engaibatis schultzei (Arratia mals. The sediments that yielded this specimen et al. 2002). have been recently identified as channel lag de- The sauropods include Brachiosaurus brancai, posits. Additional microvertebrate material was Janenschia robusta, Dicraeosaurus sattleri and recently collected in the Dwanika stream section Barosaurus afvicanus (Janensch 1961). Fossilifer- (Heinrich et al. 2001). Several samples have ous deposits exposed at Nambango (approxi- yielded teeth of a dwarf crocodile (Bernissartia mately 15 km southeast of Tendaguru Hill) that sp.; e.g., Dwa 6b/l), teeth and jaw fragments of probably belong to the Upper Saurian Bed supposed sphenodontid lepidosaurs (e.g., Dwa yielded two anterior dorsal vertebrae of a sauro- A), and a tiny dentary fragment of a mammal pod assigned to Tendaguria tanzaniensis (Bona- (Dwa 6b/l) that is too poorly preserved for de- parte et al. 2000). The ornithischians are re- tailed taxonomic identification (Heinrich et al. presented by Kentrosaurus aethiopicus, the 2001). Many microvertebrate remains are inde- theropods by Elaphrosaurus bambergi, ‘Megalo- terminable because of their poor state of preser- saurus ingens’, ‘Labrosaurus stechowi’ and ‘Cer- vation. atosaurus roechlingi’ (Janensch 1925b, see also A remarkably similar vertebrate fauna was re- Table 2). covered from the transitional sands overlying the The Upper Saurian Bed exhibits the same Trigonia smeei Bed, here considered as the base principal preservational categories of dinosaurs of the Upper Saurian Bed. Dinosaurs are mainly as the Middle Saurian Bed. Incomplete skeletons represented by isolated limb bones of Brachio- (e.g., Burosaurzu afrzcanus, site k), partial skele- saurus brancai, Barosaurus africanus, Barosaurus tons (e.g., Janenschia robusta, site G),bone fields gracilis (Janensch 1961) and Kentrosaurus aethio- (e.g., Kentrosaurus aethiopicus, site X) and soli- picus (Hennig 1925). Tendaguru site MD pro- tary bones have been found (Heinrich 1999a). duced many pterosaur remains embedded close Disarticulated skeletal assemblages of sauropods to a vertebral column of Barosaurus africanus appear to be the most common type. Single-indi- (Reck 1931). Hennig (1914b) reported four teeth vidual bone assemblages (e.g., site cc: Brachio- of the neoselachian Sphenodus sp. recovered saurus brancai) and multi-individual assemblages from the base of the Upper Saurian Bed at site Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 37

Om, and teeth of an indeterminate crocodile marine to non-marine. This indicates that hybo- were found at the same locality (Janensch, un- donts could tolerate wide ranges of salinity and, published). by Late Jurassic times, were, in some cases, adapted to brackish and fresh water conditions Flora in coastal habitats (e.g., Patterson 1966, Duffin Most samples from this unit are palynologically 1985, Duffin & Thies 1997). barren or contaminated by Recent or sub-Re- The environmental adaptations of fossil neose- cent palynomorphs (Rhizophagites assemblage). lachians are controversial. Generally, fossil neo- One sample (Dwa 5base) has yielded a small selachians are supposed to be absent from true Mesozoic palynoflora dominated by Classopollis, brackish or fresh water deposits (Thies 1995). as well as Araucariacites and a bisaccate as sub- Late Jurassic batoids, however, are the dominant ordinate components. No marine palynomorphs faunal elements in several Kimmeridgian and were observed, but charophytes are present in Tithonian neoselachian faunas from northwes- Dwa 6b, 6c and 7b. tern France and England, and have been inter- A few cuticle specimens of the Cheirolepidia- preted as having occurred in restricted lagoonal ceae and a single cuticle of araucarian type were environments (Candoni 1995, Underwood & recovered. Wood, represented by a limited Ward in press). A selachian assemblage contain- amount of well-preserved fusain in Dwa 7, is re- ing only hybodonts and batoids, but no other ferred to Glyptostroboxylon and the undescribed neoselachians has been reported from the Pur- araucarian wood type already mentioned from beckian of southern England (Underwood & the Trigonia smeei Bed. Rees in press), and is interpreted as a typical fauna of restricted environments. Typical Cretac- Environmental interpretation eous near- and/or in-shore selachians are orecto- As for the Middle Saurian Bed, most of the sedi- lobiforms, sclerorhynchids and small batoids ments of the basal Upper Saurian Bed are (e.g., Williamson et al. 1993). Extant sharks and thought to represent tidal flat deposits. The mi- rays are quite common in tidal marshes and tidal critic dolomites can be attributed to a mixing-zo- swamps, and, for example, are represented by ne or supratidal evaporitic dolomitization.The re- several species of orectolobiforms, carcharhinids markably high degree of articulation of faunal (including large specimens of hammerheads and assemblages dominated by E. cutleri demonstra- tiger sharks), and rays. The fossil neoselachian tes that post-mortem transport of shells was not Sphenodus has no Recent analogue. Hennig significant in these samples. The close correspon- (1914b) interpreted this shark as a scavenger, dence in composition and structure to the Eo- and Thies & Reif (1985) characterised it as a rniodon assemblages from the Middle Saurian slow swimming, near bottom predator. Alto- Bed suggests similar environmental conditions, in gether, the Tendaguru selachian fauna represents particular environmental stress induced by fluc- an assemblage typical of marginal marine to in- tuating and/or lowered salinities that occurs, for shore environments, and its abundant hybodonts example, in brackish water ponds. The influence as well as the numerous remains of the bony fish of freshwater is also compatible with the rare oc- Lepidotes were well adapted to cope with re- currences of charophytes and the ostracod genus duced salinities and salinity fluctuations. Cypridea. The presence of marine invertebrates, The terrestrial vertebrates of the Upper Saur- albeit sporadic, suggests proximity to the sea. ian Bed are characterised by an even more di- The unfossiliferous sandstones in the upper verse assemblage of herbivorous sauropods than part of the unit were most probably deposited in that from the Middle Saurian Bed. Again, there tiny fluvial channels in a coastal plain environ- are high-browsers (e.g., Brachiosaurus brancai) ment, whereas the argillaceous deposits are and low-browsers (Kentrosaurus aethiopicus). thought to have formed in small lakes and pools. The abundance of disarticulated skeletons sug- The selachian association from Dwa 5a, domi- gests considerable pre-burial carcass decay. With nated by three hybodont taxa and a single ba- respect to the upright, articulated fore and hind toid, is considered here as typical of nearshore feet, Janensch (1914b: 249) supposed that these environments (hybodont-batoid association), and sauropods became mired in the mud of shallow hybodonts clearly outnumber all other selachian water lagoons. He suggested that they tempora- taxa in these associations. Late Jurassic to Early rily entered such lagoons during low tides where Cretaceous hybodonts have been reported from they became trapped in the mud and killed by a wide variety of environments ranging from the returning sea. The foot bones remained in 38 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds the mud, whereas the remaining parts of the car- Trigonia schwarzi Bed casses were dispersed by wave action or wave- induced currents. The unusual upright burial of Facies foot bones testifies to their autochthony and de- In the Tendaguru area, only the basal part of the monstrates conclusively that at least some large Trigonia schwarzi Bed is preserved. The unit sauropods inhabited or certainly visited the Ten- starts with a conglomerate horizon that overlies daguru coastal plains. This is consistent with nu- an erosional contact. The succeeding trough merous reports of sauropod tracks around large cross-bedded or ripple cross-bedded, medium- to water bodies (e.g., Lockley 1991), demonstrating fine-grained sandstones form small fining-upward that sauropods visited these environments. sequences. These in turn are overlain by ripple Mass accumulations of bones of Kentrosaurus cross-bedded, horizontally bedded or biotur- aethiopicus at site X were originally interpreted bated, fine-grained sandstones, siltstones and as evidence of sudden mass death events (Ja- claystone. nensch 1914b, Hennig 1925; cf Middle Saurian Bed). However, no sedimentological indicators Invertebrates for catastrophic events have so far been found in Apart from a few disarticulated shells of Trigo- the Upper Saurian Bed. Therefore, “normal” an- niid bivalves found in coarse-grained sediments, nual input of bones might well have been re- no invertebrate fauna was found on the top of sponsible for this type of bone accumulation. Tendaguru Hill. Lange (1914) and Dietrich Several theropod species lived alongside the (1933) reported bivalve accumulations, domina- herbivorous dinosaurs, among them the medium- ted by Tancredia tellina, from poorly cemented sized, agile Elaphrosaurus bambergi and heavy- sandstones. built predators (‘Megalosaurus ingens’, ‘Cerato- saurus roechlingi’). The small mammal Bran- Vertebrates catherulum tendagurense and the sphenodontid The only known vertebrate fossils from the Tri- lepidosaurs were terrestrial while the air was gonia schwarzi Bed were found at some distance dominated by pterosaurs. Crocodiles had a semi- from Tendaguru Hill. They comprise the tooth of aquatic lifestyle and most likely fed on fish and a pycnodontid fish collected at locality 25 (Mi- other vertebrates. kadi) and an indeterminate selachian spine from As the occurrence of herbivorous dinosaurs is site 32 (Nambawala, Pilepile) (Hennig 1914b). essentially controlled by vegetation, the greater diversity of sauropods “suggests that a greater Flora diversity of vegetational growth and growth le- The Trigonia schwarzi Bed yielded two palynolo- vels were being tapped’ (Russell et al. 1980: gically productive samples (Nam la, b) from the 172). Composition of the flora indicates that a Namunda Plateau a few kilometers south of Ten- Cheirolepidiaceae-dominated terrestrial vegeta- daguru Hill. Marine dinoflagellates are rare, and tion continued to exist throughout the time of among the land-derived sporomorphs Classopol- deposition of the Upper Saurian Bed, but little lis (Cheirolepidiaceae) continues to be the most can be said about the actual diversity or compo- common form. Pteridophytic spores are characte- sition of niches. It is important to note that the rised by the appearance of striate (Cicatricosis- environments represented by the Middle and porites) and spinose types. Data on plant meso- Upper Saurian Beds were, at best, only poorly fossils are not yet available. vegetated and do not correspond to the feeding grounds of herbivorous dinosaurs. However, the Environmental interpretation plant remains transported into the environments The fining upward sequences are interpreted as of the Saurian beds and inferences regarding the tidal channel fills, whereas the fine-grained sand- feeding habits of dinosaurs make it possible to stones to claystones are thought to represent ti- deduce indirectly some characteristics of the ve- dal flat deposits. Clearly, further palaeoenviron- getated hinterland. mental analyses of coeval strata are necessary to better understand the environments and habitats represented by the Trigonia schwarzi Bed. The spore assemblage reflects a change in the composition of the terrestrial vegetation and the appearance of humidity-loving ferns with affinity to the Schizaeaceae. Mitt. Mus. Nat.kd. Berl., Geowiss. Reihe 5 (2002) 39

Palaeoenvironmental discussion the marine environment and acted as favourable sites for the accumulation of vertebrate remains. Previous interpretations Our model (see below) favours a palaeoenvir- onmental setting that is basically similar to that According to Janensch (1914b) the depositional proposed by Dietrich (1925) and Reck (1925) in environments of the Saurian beds were shallow so far as its marine aspects are reminiscent of a water lagoons, in which sedimentation was af- large lagoon that formed behind barriers. Land- fected by tides, hurricans, waves and earth- ward, the extended tidal flats bordering the la- quakes. Dietrich (1925) and Reck (1925) envi- goon gradually passed into a low-relief coastal saged a low-relief coastal plain with extended plain environment with lakes, pools and small swamps or coastal lagoons. Dietrich (1933) inter- fluvial channels. However, sedimentary indica- preted the Saurian beds as lagoonal-estuarine tors for hypersaline conditions (evaporite miner- deposits, while Reck (1925) argued for a deposi- als, evaporite pseudomorphs, intense mud- tion in hypersaline lagoons or saline marshes. cracks), as proposed by Reck (1925), were not Conversely, Fraas (1908), Schuchert (1918), found. Similarly, in contrast to Dietrich (1925), Abel (1927), Parkinson (1930) and Colbert indicators for the existence of swamps (root (1984) believed that an estuarine environment traces, paleosols with indicators of waterlogging, with rivers and deltas existed in what is now the coal seams) are also missing. Tendaguru area. The dinosaurs lived primarily on land and along river banks and adjacent re- gions possibly including “brackish water marshes A refined model for the Tendaguru Beds along the coast and rivers” (Schuchert 1918: 275). Carcasses of drowned or killed dinosaurs Litho- and biofacies of the Tendaguru Beds indi- floated downstream in rivers that meandered cate a marginal marine setting, composed of (1) through coastal lagoons, and the carcasses were lagoon-like, shallow marine environments; (2) buried close to the mouths of rivers. extended siliciclastic tidal flats and low-relief By contrast to the assumption of an estuarine coastal plains; and (3) vegetated hinterlands. or deltaic environment for the Saurian beds, we These three environmental sub-units are dis- found no indicators for the existence of major cussed in more detail below (Fig. 6): fluvial systems in the Tendaguru area. Deposits typical of large fluvial or distributary channels Lagoon are missing, as are other sediments characteristic Based on our sedimentological, taphonomic and of deltas, such as distributary mouth bar sands or palaeoecological observations, the Nerinea Bed, subaqueous slump deposits (Coleman & Prior Trigonia smeei Bed and Trigonia schwarzi Bed 1982, Elliott 1986). Furthermore, coarsening-up- probably represent a lagoon-like, coastal, shallow ward sequences, typical of delta deposits, are not marine environment above fair weather wave developed, and the sediments generally become base that was affected by tides and storms. The finer grained towards the shoreline. This argues lagoon was separated from the open sea by bar- against the presence of a major sediment source riers such as ooid bars, sand bars or sandy bar- in the direct hinterland of the Tendaguru region rier islands. With its effective tidal passes, strong and favours transport parallel to the shoreline tidal currents and adjacent tidal flats, it probably for the relatively coarse-grained sandstones of resembled an extensive “leaky lagoon” (Kjerfve the Nerinea, the Trigonia smeei and the Trigonia & Magill 1989). Water agitation ranged from mo- schwarzi Bed. Similarly, deposits typical of estu- derately high on lower tidal flats to very high in aries are missing. Consequently, the assumption tidal channels, sand bars and reworked horizons. of a major river coming from the hinterland and Clearly, energy levels were sufficiently high to entering the sea in the Tendaguru region must keep food particles in suspension, as is demon- be rejected, and long-distance transport of large strated by the dominance, throughout, of suspen- vertebrate carcasses in rivers, as suggested by sion-feeders. The general absence or scarcity, at Schuchert (1918), is unlikely. Nevertheless, the least during most periods, of stenohaline higher occurrence of small-scale channel fills in the taxa such as ammonites, articulate brachiopods, Upper Saurian Bed indicates the existence of in situ corals and echinoderms is striking. This some minor river systems in the coastal plain. points to salinity conditions that deviated from These rivers might have transported some small the normal marine condition. Salinity reductions vertebrate-carcasses from the continental into or fluctuations, however, seem to have been of 40 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds

Fig. 6. Environmental model of the Tendaguru Beds at their type locality. HWL = high water line; LWL = low water line. For discussion see text. minor extent as is indicated by the moderately come from marine influenced sediments there is high diversity of macro- and microinvertebrates. no evidence of salt-tolerance by any of the fossil By contrast, normal marine salinities are likely plants found at Tendaguru. Therefore, the feed- for the coral-oyster biostrome (Trigonia smeei ing habitats and place of final burial of large ter- Bed) at some distance from Tendaguru and in restrial vertebrates do not coincide. We envisage the basal part of the Nerinea Bed. periods of seasonal drought that drastically re- duced the wide variety of vegetational food re- Tidal flats and coastal plains sources in the Tendaguru hinterland. As a conse- The fine-grained sediments of the Lower, Middle quence, the herbivorous dinosaurs left their and Upper Saurian Beds and their biota are in- previously vegetated “home lands” and, followed terpreted as representing largely intertidal depo- by carnivorous dinosaurs, were forced to move sits and low-energy coastal lakes and ponds. In to nearby coastal plains and tidal flats in search part, continental conditions also prevailed, such of food and water. In these apparently poorly as sabkha-like coastal plains with lakes and vegetated environments, the animals were ex- pools, some of which seem to have dried up peri- posed more intensively to direct sunlight, but, at odically and small fluvial channels. High densi- the same time, these areas most likely offered ties of Eomiodon in very low diversity assembla- water holes that could be used as muddy wal- ges occur at various levels within the sequence, lows by dinosaurian megaherbivores (e.g., Bra- most commonly at the base of the Middle and chiosaurus, Barosaurus, Dicraeosaurus) for ther- Upper Saurian Beds. They reflect environmental moregulation, especially for dumping absorbed stress related to abnormal salinity conditions. heat. Nevertheless, an increased mortality rate Considering the marked seasonality of the cli- during periods of seasonal drought is to be ex- mate (see below), seasonally fluctuating salinity pected. Therefore, wallows and ephemeral water values are assumed rather than a relatively con- bodies such as lakes and ponds might have acted stant reduction of salinities over longer periods as both refuges and die-off sites for migrating of time. These salinity fluctuations may have be- dinosaurs during periods of seasonal drought en due to freshwater influx from the land in are- (Heinrich 1999a). as adjacent to the Tendaguru area, heavy seaso- nal rainfall, or a combination of both. Vegetated hinterland These are also the environments in which the Vegetation in the hinterland can be inferred indi- large vertebrate remains are preserved. How- rectly from plant material that was transported ever, both tidal flats and marginal areas of the into the marginal marine system either by water coastal plains apparently lacked substantial vege- or by wind. It is characterised by a diverse coni- tation. Although all the palaeobotanical remains fer flora, which, together with spore-producing Mitt. Mus. Nat.kd. Berl.. Geowiss. Reihe 5 (2002) 41 plants, apparently formed part of the food sour- With respect to palaeovegetation, the conifer ce of the large herbivorous sauropods. The most family Cheirolepidiaceae, represented in the important group are the Cheirolepidiaceae, Tendaguru Beds by both mesofossils and land- which, by Late Jurassic times, are well known as derived palynofloras, is regarded as a thermophi- a dominant element in forests bordering the sea lous group with xerophytic adaptations (Watson as well as on better drained soils in the uplands 1988). The occurrence of growth rings demon- (Alvin 1982). Further common elements of the strates that climatic conditions varied frequently. flora comprise Podocarpaceae, Araucariaceae For the Tendaguru climate, dry seasons are sug- and yet undescribed conifers. Cycads and gink- gested by the extensive occurrence of fossil char- gos are less commonly preserved. Undergrowth coal (see Batten 1975). On the other hand, abun- is more difficult to reconstruct and may be repre- dance of as yet undescribed fungi infesting and sented by shrub-like Cheirolepidiaceae, several degrading the wood requires wet conditions or pteridophytes (e.g., P1. 1: 8) and by pterido- at least increased humidity (Alvin et al. 1981). sperms of the family Corystospermaceae. Seasonal humidity is also indicated by the occur- According to climate models (see below), in rence of Glyptostrobus- and Podocarpus-related the western direction the vegetated area passed wood (Figueiral et al. 1999), which is present in into the dry interior of Gondwana. Obviously, all units of the Tendaguru Beds. Spores of the this region was highly unfavourable as a refuge generally hygrophilous pteridophytes are rare during periods of seasonal drought, and dino- and of relatively low diversity. The appearance saurs were more likely displaced eastward to- in the Trigonia schwarzi Bed of Cicatricosispor- wards the sea. ites and related taxa signals a rather moderate diversification of pteridophytic spores during Ve r t ic a1 s u cce s s ion Early Cretaceous times. This is tentatively inter- In vertical sequence, the Tendaguru Beds consist preted as a change towards slightly more humid of three transgressive-regressive cycles. During conditions. In summary, a subtropical to tropical transgressive periods, the coastal barrier systems palaeoclimate, characterised by seasonal rainfall migrated landward and caused large-scale re- alternating with a pronounced dry season, pre- working of tidal flat and coastal plain deposits. vailed throughout most of the depositional inter- Subsequent regressive sequences demonstrate an val of the Tendaguru Beds. Mineralogical and almost complete succession from shallow subti- palynological data from the Trigonia schwarzi dal sands to tidal flat and beach sediments, follo- Bed both seem to indicate a shift towards a wed by sabkha-like coastal plain deposits (Bus- more humid climate in Early Cretaceous times. sert & Aberhan 2001). Generally, our results are in good agreement with results of other workers. Based on sedimen- tological and palaeontological evidence, Hallam Climate (1985, 1993) proposed a dry climate for East Africa during the Late Jurassic, and climate pre- Information regarding the climate can be drawn dictions based on GCM simulations by Moore from a variety of sources. The prevalence of sili- et al. (1992), Valdes & Sellwood (1992) and ciclastic sediments and reduced salinities, as de- Valdes (1994) suggested a strong seasonal preci- duced from the composition of fauna and micro- pitation for the region. In marked contrast, Uh- flora, reflect considerable freshwater input, mann (1996), who used lithological and minera- either by rivers or by strong precipitation. By logical indicators, proposed a humid climate for contrast, high amounts of feldspars in the sand- southwestern Madagascar during the Upper Jur- stones, and the dominance of smectite and illite assic and argued for an exceptional climate in the clay mineral fractions indicate a reduced (“klimatische Sonderstellung”) for Madagascar intensity of chemical weathering. Furthermore, during this interval. the presence of calcretes and supratidal dolo- mites provide evidence of dry periods under a warm to hot climate with seasonal rainfall. High- Conclusions er potassium feldspar/plagioclase feldspar-ratios in the sandstones of the Trigonia schwarzi Bed, Within the scope of an interdisciplinary analysis as compared to the Jurassic part of the sequence, of the Tendaguru Beds (Late Jurassic to Early might be related to an increase in chemical Cretaceous of Tanzania, East Africa), we utilized weathering and a more humid climate. new sedimentological and palaeontological data 42 Aberhan, M. et al., Palaeoecology of the Tendaguru Beds to construct an environmental model for the Acknowledgements Tendaguru Beds at their type locality. In our We would like to thank Abdul H. Mruma and Sospeter Mu- model we recognise three main palaeoenviron- hongo from the Department of Geology of the University of mental units: (1) tide- and storm-dominated, la- Dar es Salaam for their participation in and support for the goon-like, shallow marine environments repre- Tendaguru Expedition 2000. We wish to thank Oliver Hampe, Museum fiir Naturkunde, Gerhard Maier, Calgary, sented by the Nerinea, Trigonia smeei and Emma Msaky, Tanzania Petroleum Development Corpora- Trigonia schwarzi beds. The various subenviron- tion, Dar es Salaam, and Remigius Chami, Ministry of Natur- ments comprise barriers such as ooid bar and al Resources and Tourism, Antiquities Units, Dar es Salaam, for accompanying us in the field. siliciclastic sand bar complexes, tidal channels Many thanks go to Hans-Peter Schultze, Museum fur Nat- and tidal sand bars, flood and ebb deltas and urkunde, for supporting the project and presenting it to dif- beach sands. Generally, the lagoon was subject ferent German commissions. We are very grateful to Andrew R. Milner, London, for his help with the identification of mi- to minor salinity fluctuations. Landwards, the la- crovertebrates (lissamphibians, sphenodontids). We thank goon passed into (2) extended siliciclastic tidal Gunter Schweigert, Staatliches Museum fur Naturkunde flats and low-relief coastal plains that are largely Stuttgart, for the discussion of stratigraphic issues and Mi- chael Schudack, Freie Universitat Berlin, for the determina- represented by the three dinosaur-bearing suc- tion of charophytes. Photographic and graphic assistance was cessions, i.e. the Lower, Middle and Upper Saur- provided by Jorg-Peter Mendau, Carola Radtke and Elke ian Beds. Subenvironments include low-energy, Siebert, all Museum fur Naturkunde. This study was financially supported by grants from the brackish coastal lakes and ponds, as well as Deutsche Forschungsgemeinschaft, which are acknowledged pools and small fluvial channels in coastal plains. with gratitude. The research of JK has been supported by a As the preserved parts of the coastal plain lack Marie Curie Fellowship of the European Community pro- gram “Improving Human Research Potential and the Socio- any signs of an autochthonous vegetation, the economic Knowledge Base” under contract number HPMF- place of final burial and feeding grounds of large CT-2001-01310. Camping and technical equipment was do- land-dwelling vertebrates do not coincide. nated by the firm of BIWAK, Berlin-Kopenick, and by the TOOL-CO firm, Berlin-Lichtenrade. Throughout much of their lives, dinosaurs appar- Finally, we would like to thank the reviewers Franz T. Fur- ently thrived in (3) a vegetated hinterland. The sich, Universitat Wurzburg, Wolfgang Mette, Universitat In- floral composition of the latter can only be in- nsbruck, and Dave Unwin, Museum fur Naturkunde, for ferred indirectly from plant material transported their comments on the manuscript. into the marine-influenced environments, and re- construction is hampered by the selective preser- References vation of only the most durable plant remains. This region of the Tendaguru palaeo-ecosystem Abel, 0. 1927. Lebensbilder der Vorzeit. 637 pp., Fischer, Jena. was covered by a diverse conifer flora, which, Aitken, W. G. 1961. Geology and palaeontology of the Juras- along with cycads, pteridophytes and ginkgos, at sic and Cretaceous of southern Tanganyika. - Geological Survey of Tanganyika Bulletin 31: 1-144. least partly served to meet the immense food re- Alvin K. L. 1982. Cheirolepidiaceae: biology, structure and quirements of large sauropods. Various sedimen- paleoecology. - Review of Palaeontology and Palynology 37: 71-98. tological and palaeontological features of the Alvin K. L., Fraser C. J. & Spicer R. A. 1981. Anatomy and Tendaguru Beds suggest that these Late Jurassic palaeoecology of Pseudofrenelopsis and associated coni- sediments were deposited under a subtropical to fers in the English Wealden. - Palaeontology 24: 759-778. tropical palaeoclimate, with seasonal rainfall al- Arratia, G. & Schultze, H.-P. 1999. Semionotifonn fish from ternating with a pronounced dry season. In the Upper Jurassic of Tendaguru (Tanzania). - Mitteilun- Early Cretaceous times, climate seems to have gen aus dem Museum fiir Naturkunde Berlin, Geowis- senschaftliche Reihe 2: 135-153. shifted towards more humid conditions. Arratia, G., Kriwet, J. & Heinrich, W.-D. 2002. 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