Hubbry Logo
Elrhaz FormationElrhaz FormationMain
Open search
Elrhaz Formation
Community hub
Elrhaz Formation
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Elrhaz Formation
Elrhaz Formation
Elrhaz Formation
View on Wikipedia
from Wikipedia

The Elrhaz Formation is a geological formation in Niger, West Africa.

Key Information

Its strata date back to the Early Cretaceous, about 125 to 112 million years ago. Dinosaur remains are among the fossils that have been recovered from the formation, alongside those of multiple species of crocodyliformes.

Gadoufaoua

[edit]
Reconstructed skeleton of an anhanguerid from the formation

Gadoufaoua (Tuareg for "the place where camels fear to go") is a site within the Elrhaz Formation (located at 16°50′N 9°25′E / 16.833°N 9.417°E / 16.833; 9.417) in the Tenere desert of Niger known for its extensive fossil graveyard. It is where remains of Sarcosuchus imperator, popularly known as SuperCroc, were found (by Paul Sereno in 1997, for example), including vertebrae, limb bones, armor plates, jaws, and a nearly complete 6 feet (1.8 m) skull.

Dinosaurs of Elrhaz formation
A spinosaurid claw from the Elrhaz formation

Gadoufaoua is very hot and dry. Based on the sedimentary and fossil record, Gadoufaoua had trees, plants, and wide rivers 112 million years ago. The river covered the remains of dead animals, the fossilized remains of which were protected by the drying rivers over millions of years.[1]

Vertebrate paleofauna

[edit]

Chondrichthyes

[edit]
Chondrichthyes
Genus Species Material Notes Images
Hybodus[2] H. sp. Dorsal spines[2]

Sarcopterygii

[edit]
Sarcopterygii
Genus Species Material Notes Images
Asiatoceratodus[2] A. tiguidiensis[2] Dipnomorph fish. Originally described as Ceratodus tiguidiensis,[3] assigned to Arganodus by M. Martin (1984)[4] and reassigned by Kemp (1998) to the genus Asiatoceratodus.[5]
Mawsonia[6] M. tegamensis[6] A small species.[7]
Neoceratodus[2] N. africanus[2] Tooth plates.[8] Dipnomorph fish. Originally described as Ceratodus africanus, assigned to Neoceratodus by M. Martin, 1982.[9]
Neoceratodus forsteri, a modern species

Actinopterygii

[edit]
Actinopterygii
Genus Species Material Notes Images
Pliodetes[10] P. nigeriensis[10] Skull and postcranial material including body scales.[11] Originally thought to be a semionotid, later assigned to Lepisosteoidei.[11]
Pycnodontidae indet.[2] Indeterminate

Testudines

[edit]
Testudines
Genus Species Material Notes Images
Francemys[12] F. gadoufaouaensis[12] "Shell of a juvenile individual and several articulated and disarticulated plates."[12] Pelomedusoid turtle. Named in honour of France de Lapparent de Broin.[12]
Taquetochelys[13] T. decorata[13] A few disarticulated plates and nearly complete skeleton.[14] Araripemydid turtle, similar in shell size to South American Araripemys (20–30 cm). Laganemys tenerensis was synonymysed with Taquetochelys by Pérez-García, 2018.[14]
Teneremys[13] T. lapparenti[13] "Several relatively complete skeletons."[12]

Crocodyliformes

[edit]
Crocodyliformes
Genus Species Material Notes Images
Anatosuchus[15] A. minor[15] "Nearly complete skull"
Araripesuchus[15] A. wegeneri[15] "Nearly complete skull"
Sarcosuchus[16] S. imperator "Partial skeletons, numerous skulls"
Stolokrosuchus S. lapparenti

Dinosaurs

[edit]

Ornithischians

[edit]
Ornithischians
Genus Species Material Notes Images
Elrhazosaurus[15] E. nigeriensis[15] "Femora."[17] A dryosaurid
Lurdusaurus[15] L. arenatus[15] "Partial skull, fragmentary postcranial skeleton."[18]
Ouranosaurus[15] O. nigeriensis[15] "Skull and poscrania, second skeleton."[19]

Theropods

[edit]
Theropods
Genus Species Material Notes Images
Afromimus A. tenerensis "caudal vertebrae, chevrons and portions of the right hind limb"[20] A putative noasaurid[21]
Cristatusaurus[22] C. lapparenti[22] Jaw bones and vertebral fragments.[22] A spinosaurid potentially synonymous with Suchomimus[23]
Eocarcharia[15] E. dinops[24] "Partial skull and postcranial remains."[25] Known from chimaeric remains; the holotype and skull roof material likely derive from a baryonychine spinosaurid, while the referred maxilla is from a carcharodontosaurid.[26]
Kryptops[15] K. palaios[15] Postcranial skeleton and partial skull.[27] An abelisaurid
Suchomimus[15] S. tenerensis[15] Partial skull and associated skeleton.[28] A baryonychine spinosaurid

Sauropods

[edit]
Sauropods
Genus Species Material Notes Images
Nigersaurus N. taqueti Skull and skeletal remains A rebbachisaurid.

Flora

[edit]
Plants
Genus Species Material Notes Images
Paradoxopteris[29] P. stromeri A tree fern and member of Matoniaceae.
Protophyllocladoxylon P.chudeaui A conifer[29]

See also

[edit]

References

[edit]

Further reading

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Elrhaz Formation

View on Grokipedia
from Grokipedia
The Elrhaz Formation is a Lower in the Iullemmeden Basin of the Republic of , , dating to the Aptian-Albian stages approximately 116 to 113 million years ago, and renowned for its rich vertebrate fossil record that includes multiple taxa alongside crocodyliforms, , fish, and pterosaurs. Composed predominantly of cross-bedded, medium-grained fluvial sandstones with intercalated clays, limestones, and shales, the formation reaches a thickness of 80 to 120 meters and represents a continental depositional environment characterized by river channels and floodplains in a semi-arid to tropical setting. It forms part of the broader Tégama Group, with its lower boundary conformably overlying the Tazolé Formation and its upper boundary transitioning into the Echkar Formation, and the type section is located near the town of Elrhaz at the prominent Gadoufaoua paleontological site along the western margin of the Ténéré . The formation's three informal members reflect variations in lithology and depositional : the lower and middle members feature more clay-rich and intervals with minor limestones indicative of overbank deposits, while the upper member is dominated by shaly and sandstones, consistent with overbank or lacustrine within a fluvial-dominated system. First documented in the mid-20th century through French geological surveys, the Elrhaz Formation gained international prominence in the and due to expeditions led by paleontologists such as Philippe Taquet and Paul Sereno, which uncovered exceptionally preserved skeletons that have advanced understanding of terrestrial ecosystems in . Paleontologically, the Elrhaz Formation is one of Africa's most productive sites, yielding fossils of theropod dinosaurs such as the spinosaurid tenerensis, a long-snouted piscivorous predator up to 11 meters in length with a low dorsal sail, described from multiple partial skeletons including a well-preserved . Other notable theropods include the allosauroid Afrovenator abakensis, the carcharodontosaurid Eocarcharia dinops, and the abelisaurid Kryptops palaios, representing basal members of major carnivorous dinosaur clades that highlight early diversification in Africa. Among herbivores, the rebbachisaurid sauropod Nigersaurus taqueti stands out for its highly specialized, wide-mouthed adapted for low-level grazing on ferns and horsetails, with over 500 replaceable teeth in its battery-like dentition. The formation also preserves remains of the gigantic crocodyliform Sarcosuchus imperator, a 12-meter-long semiaquatic predator nicknamed "SuperCroc," alongside smaller notosuchians and pholidosaurids, illustrating a complex riparian . These discoveries underscore the Elrhaz Formation's role in documenting faunal connections between African and South American biotas during the breakup of .

Geology

Stratigraphy

The Elrhaz Formation belongs to the Tégama Group within the geological framework of the Ténéré region, representing a key unit in the sedimentary sequence of . This group encompasses terrestrial deposits that reflect continental depositional environments across the . Stratigraphically, the Elrhaz Formation overlies the Tazolé Formation, characterized by coarse sandstones, and is conformably overlain by the Echkar Formation, marking a progression from lower to upper units within the Tégama Group. Thickness varies regionally, measuring approximately 80 meters at the type section in the Gadoufaoua area, reaching up to 120 meters in the southeast, and thinning toward the northeast due to depositional and erosional patterns. Internally, the formation is subdivided into three members within its predominantly sandstone-dominated sequence: a lower member of black, purple, or red clays interbedded with black limestones; a middle member consisting of coarse, cross-bedded sandstones; and an upper member of shaly, calcareous sediments. The Elrhaz Formation correlates with other continental deposits in , particularly equivalent to portions of the Tagrezou Formation in the Téfidet Sub-Basin of the larger Niger Basin system. It forms part of the broader Continental Intercalaire, a widespread suite of terrestrial sediments, and exhibits potential stratigraphic links to the in through shared Early to mid-Cretaceous age ranges and regional tectonic continuities across northern .

Lithology

The Elrhaz Formation consists predominantly of fine- to medium-grained, cross-bedded fluvial sandstones, with intercalated overbank clays, mudstones, and minor limestones. These sandstones form the primary , exhibiting channel structures such as trough and planar cross-stratification, indicative of riverine deposition with higher-energy flow regimes in channels and lower-energy fines in adjacent floodplains. The formation reaches thicknesses of up to 120 in southeastern exposures, thinning northeastward, and is divided into three informal members: a lower member of black, purple, or red clays interbedded with black limestones; a middle member consisting of coarse, cross-bedded sandstones; and an upper member of shaly, sediments. Oblique stratifications and occasional barite nodules are common sedimentary features throughout. The channelized sandstone banks, often alternating with , reflect a depositional system of meandering rivers, where coarser channel sands represent active fluvial transport and finer overbank deposits indicate periodic flooding. This lithologic arrangement contributed to favorable taphonomic conditions for preservation, particularly through rapid in sandy channel fills that protected articulated skeletons from prolonged exposure and scavenging. Microvertebrate remains, such as teeth and scales, show high fragmentation consistent with moderate hydrodynamic reworking in these dynamic fluvial settings.

Location and History

Geographic Setting

The Elrhaz Formation is primarily exposed in the Ténéré Desert of central , , within the . The formation's main outcrops occur in the Gadoufaoua area, centered at coordinates approximately 16°42′N 9°20′E. These outcrops cover several hundred square kilometers, with fossiliferous strata extending over a length of about 180 km and a width of roughly 2 km, encompassing an area of approximately 360 km². The formation is situated south of the Air Mountains and embedded within the vast sand sea, a expansive erg of dunes that dominates the regional landscape. Access to the Elrhaz Formation's exposures presents substantial logistical challenges for fieldwork, stemming from the site's extreme remoteness in the heart of the Desert, where temperatures often exceed 125°F (52°C) and water sources are scarce. Additionally, political instability in , including Sahelian unrest, has periodically disrupted expeditions and heightened security risks in the region.

Discovery and Research

The Elrhaz Formation was first identified during mid-20th-century French geological surveys in colonial , which mapped the broader Continental Intercalaire supergroup and noted its basic stratigraphy in the Ténéré Desert region. These early explorations, conducted by geologists such as Albert-Félix de Lapparent in the 1950s and 1960s, focused on hydrocarbon potential and established the formation's position within the Lower (Aptian-Albian) Tégama Group, primarily through outcrop descriptions in areas like Gadoufaoua. Paleontological research intensified in the and through French-led expeditions that uncovered fossils, with Philippe Taquet playing a pivotal role in documenting the formation's rich . Taquet's teams discovered significant remains, including the first nearly complete skeletons of the iguanodontian nigeriensis in 1965 and 1970 at Gadoufaoua, which he formally described in 1976 and used to refine the formation's . These efforts, supported by institutions like the Centre National de la Recherche Scientifique (CNRS), highlighted the site's potential as a key locality and spurred further stratigraphic correlations across . In the 1990s, American-led expeditions under Paul Sereno marked a major expansion of research, yielding landmark discoveries that elevated the Elrhaz Formation's global significance. Sereno's Project Exploration teams, beginning in 1993 and intensifying through the decade, excavated at Gadoufaoua and nearby sites, uncovering the spinosaurid tenerensis in 1997 and the giant crocodyliform imperator in the same year; these were described in 1998 and 2001, respectively, revealing insights into large-bodied predators of the Aptian-Albian. These finds, often in collaboration with Nigerien scientists, integrated the formation into broader theropod and crocodyliform phylogenies. Ongoing research has faced significant challenges since 2010, including political instability and security threats in northern that have restricted access to field sites like Gadoufaoua. Expeditions now require armed military escorts due to and regional conflicts, with a 2023 coup further delaying exports and analyses. Recent taxonomic revisions, such as those proposing lapparenti (1998) as a junior synonym of based on overlapping material from the formation, reflect continued scholarly refinement amid these logistical hurdles.

Paleobiota

Flora

The of the Elrhaz Formation is poorly documented compared to its record, but available evidence points to a diverse dominated by gymnosperms and ferns in a fluvial setting. Abundant remains of homoxylous wood, particularly the bennettitalean form Protophyllocladoxylon chudeaui, have been recovered from sites in the Gadoufaoua area, indicating the presence of woody plants adapted to riverine environments. These wood fossils suggest bennettitaleans played a significant role in the local , contributing to forested habitats along ancient waterways. Ferns are represented by silicified structures attributed to Filicales, preserved in fine-grained sediments that facilitated their mineralization. Such taphonomic conditions, including compressions and , reflect rapid burial in low-energy depositional settings near rivers, protecting delicate material from decay. The overall floral assemblage implies a warm, humid with seasonal flooding, supporting riparian forests that coexisted with localities like Gadoufaoua.

Vertebrate Fauna

The vertebrate of the Elrhaz Formation exhibits high diversity, with over 20 taxa documented from Aptian-aged deposits, particularly at the Gadoufaoua locality in . This assemblage is dominated by aquatic and semi-aquatic forms, reflecting the paleoenvironment, and includes a mix of chondrichthyans, actinopterygians, amphibians, sauropsids (such as crocodyliforms, , and dinosaurs), and other reptiles. Microvertebrate studies reveal a composition where sauropsids account for approximately 52% of identifiable remains (excluding isolated teeth and scales), actinopterygians about 33%, chondrichthyans 7%, and amphibians 7%, underscoring the prevalence of riverine and lacustrine inhabitants alongside terrestrial elements. Taphonomic patterns in the Elrhaz Formation are strongly influenced by its fluvial depositional setting, with most fossils preserved in channel sandstones and overbank clays of a dynamic river system. Remains are typically highly fragmented and disarticulated, resulting from post-mortem transport, abrasion, and erosion in high-energy fluvial environments; articulated skeletons are rare, as evidenced by isolated bones and associated but scattered elements in key sites. This bias favors durable, hard tissues from smaller or more robust animals, while larger terrestrial forms like dinosaurs are represented mainly by partial skeletons or isolated large bones. Biogeographically, the Elrhaz Formation fauna links African assemblages to broader patterns, with affinities to South American deposits such as the Santana Formation in , indicative of lingering faunal exchange following the breakup of . This connection is evident in shared microvertebrate elements, including stem-boreosphenidan mammals and actinopterygian fishes, highlighting trans-Atlantic dispersals during the . The presence of archosaurian groups further supports mid-Cretaceous trans-Tethyan distributions across northern .

Chondrichthyes

The of the Elrhaz Formation are represented by rare hybodont shark remains, including teeth and fragmentary spines assigned to an indeterminate hybodontid (Hybodontidae gen. et sp. indet.), indicating a durophagous predator specialized in crushing hard-shelled prey such as . These fossils, comprising 2-3% of the microvertebrate assemblage in channel deposits at Gadoufaoua, reflect high-energy fluvial conditions where such sharks occupied mid-level predatory niches. Complete specimens are exceedingly rare due to the poor fossilization potential of cartilage in chondrichthyans, resulting in highly fragmented and isolated elements like these calcified spines and teeth. In the riverine paleoecology of the Elrhaz Formation, the hybodontid likely preyed on smaller and , contributing to the diverse aquatic alongside bony fishes. This hybodontid is comparable to contemporaneous hybodonts in other formations, such as those from the Santana Formation of , underscoring biogeographic links between West African and northeastern Brazilian fluvial systems during the breakup of .

Sarcopterygii

The Elrhaz Formation preserves a modest diversity of sarcopterygian fishes, primarily consisting of ceratodontid lungfishes and a mawsoniid , which inhabited freshwater systems during the . These lobe-finned fishes exhibit morphological traits suited to dynamic riverine and swampy conditions, including robust for processing varied diets in vegetated, low-energy aquatic environments. Asiatoceratodus tiguidiensis, a reclassified ceratodontid previously known as Arganodus tiguidiensis or tiguidiensis, is documented from tooth plates featuring five to eight straight crests with ridges and inter-ridge perforations, facilitating the crushing of shelled and matter. This species' dental morphology, combined with the formation's depositional evidence of seasonal flooding and stagnation, underscores air-breathing adaptations via a lung-like organ, enabling survival in hypoxic swamp waters. Neoceratodus africanus, another ceratodontid , is represented by dental plates with characteristically five to seven crests radiating from the mesiolingual angle, optimized for grinding tough vegetation and small prey in shallow, oxygen-depleted settings. Like its congener, it likely relied on air-breathing to navigate the humid, low-oxygen conditions of the Elrhaz paleoenvironment, where such physiological traits would confer advantages during dry periods or in anoxic pools. Mawsonia tegamensis, the sole coelacanth species identified, is a predatory mawsoniid known from partial skulls, dermal bones, and skeletal fragments, indicating a robust build suited for ambushing smaller aquatic vertebrates in river channels. These remains co-occur with actinopterygian fishes in fluvial sandstones, highlighting its role in the formation's food web amid a humid, .

Actinopterygii

The ray-finned fishes () represent a diverse and abundant component of the Elrhaz Formation's vertebrate fauna, primarily documented through disarticulated scales and bones recovered from microvertebrate assemblages at Gadoufaoua, . These remains constitute approximately 22% of identified microvertebrate specimens, comprising 814 scales among 3703 total elements, and underscore a rich ichthyofauna adapted to the formation's fluvial systems. A notable taxon is Pliodetes nigeriensis, a semionotid (Semionotiformes) described from partial skeletons exhibiting thin, diamond-shaped body scales with peg-and-socket articulations and an edentulous (toothless) jaw. This species, characterized by reduced dermal ossifications on the and ossified vertebral centra, belongs to the broader and reflects primitive neopterygian traits combined with derived features such as a superficial premaxillary ascendent process integrated into the skull roof. As a small-bodied semionotiform, P. nigeriensis likely functioned as a schooling in shallow freshwater habitats. Indeterminate pycnodontid remains, including molariform and ovoid teeth (up to 2 mm long) with flat, wrinkled occlusal surfaces, as well as incisiform teeth (2-3 mm high), point to durophagous actinopterygians specialized for crushing shelled . These elements, such as prearticulars, vomers, and isolated from multiple specimens, suggest pycnodonts occupied niche roles in benthic feeding within the . Further diversity is evident from disarticulated bones and scales attributable to other actinopterygian groups, including ginglymodians (e.g., 58-473 teeth and 260 scales), teleosts (79-148 vertebrae), amiiforms (128-139 teeth), and ichthyodectiforms (10 teeth), indicating a multifaceted assemblage of piscivores, carnivores, and generalists. Overall, actinopterygians dominated the aquatic vertebrate community (61-68% of ), with 44% classified as freshwater taxa and 26% as amphibious, thriving in channel-type depositional environments marked by high hydrodynamism. These fishes likely served as prey for crocodyliforms and theropod dinosaurs within the broader riparian assemblage.

Testudines

The Elrhaz Formation has yielded remains of several pleurodiran turtles (Testudines: ), primarily from the GAD 5 level at Gadoufaoua in central , reflecting adaptations to the formation's fluvial and environments during the stage of the . These fossils include both semi-aquatic and potentially marginal forms, with shell morphologies suited to riverine and swampy habitats characterized by sandy fluvial deposits and periodic flooding. Francemys gadoufaouaensis, a basal member of Pelomedusoides within Pan-Pleurodira, is known from nearly complete shells measuring less than 15 cm in length, featuring a subcircular with a flattened medial region, absent keels, and dense dichotomous furrow ornamentation. This semi-aquatic species exhibits long axillary and inguinal processes along with a sutured , adaptations that facilitated mobility in fluvial settings with strong currents and supported a involving both and basking on riverbanks. Its compact shell structure suggests efficiency in navigating shallow, vegetated waters typical of the Elrhaz floodplains. Taquetochelys decorata, the sole African representative of Araripemydidae, is a small pleurodiran with a length of approximately 15–30 cm, based on isolated plates and partial skeletons including hypoplastra, costals, and peripherals. The shell displays low tubercles forming radiating ridges and a variable neural series, with the presence of mesoplastra indicating a primitive pelomedusoid suited to freshwater environments. This species likely inhabited the margins of rivers and lakes, with its lightweight, ornamented shell permitting occasional terrestrial excursions onto vegetated floodplains, though primarily adapted for aquatic foraging. Teneremys lapparenti, a podocnemidoid pleurodiran, represents a larger river-dwelling form with a low-domed shell inferred to exceed 50 cm in length, characterized by low-convexity plates and robust peripheral elements that provided streamlined protection in flowing waters. Recovered from disarticulated remains at Gadoufaoua, its broad, flattened morphology aligns with amphibious habits in swampy, settings, where it co-occurred with other aquatic vertebrates. Shell features, including a wide nuchal plate and continuous costal series, suggest an omnivorous diet incorporating and , consistent with the of related erymnochelyines.

Crocodyliformes

Crocodyliforms constitute the most diverse and abundant vertebrate group in the Elrhaz Formation, with multiple taxa adapted to the formation's swampy, low-energy fluvial paleoenvironment of braided rivers and vegetated floodplains during the Aptian-Albian stages of the Early Cretaceous. This dominance underscores the prevalence of semi-aquatic habitats that favored these archosaurs over terrestrial dinosaurs, which are less common in the preserved assemblages. The assemblage includes both longirostrine piscivores and shorter-snouted terrestrial forms, showcasing a range of feeding strategies from filter-feeding to active predation. Anatosuchus minor, a small notosuchian reaching approximately 1 meter in length, is characterized by its broad, duck-like equipped with secondary structures and marginal teeth suited for filter-feeding on small aquatic prey such as , frogs, and . Its nearly complete and partial reveal a secondary bony and U-shaped jaw margins that facilitated suction feeding in shallow waters, an adaptation unique among crocodyliforms for exploiting soft-bodied in vegetated swamps. Araripesuchus wegeneri, another notosuchian, represents a terrestrial predator with a short, robust and ziphodont indicating a carnivorous diet focused on small vertebrates and possibly scavenging. Known from multiple nearly complete skulls and skeletons preserved in close association, suggesting gregarious behavior, this species measured about 1.5 meters long and possessed strong forelimbs for digging or grappling prey on land. The giant pholidosaurid imperator stands out as the apex of the formation, attaining lengths up to 12 meters and masses exceeding 8 tons based on growth series from juveniles to adults. Its elongate snout, armed with conical teeth and a notched for grasping large , combined with a heavily armored body and powerful tail, enabled ambush hunting in rivers; osteohistological analysis reveals rapid early growth followed by sustained longevity over decades. Stolokrosuchus lapparenti, a basal neosuchian often classified within Goniopholidae or as a peirosaurid stem, features a long, slender snout with conical teeth ideal for ambush predation on in low-flow channels. Preserved by an almost complete skull exhibiting prefrontal bosses and a narrow rostrum, this medium-sized form (estimated 2-3 meters) likely lurked in vegetated river margins, its morphology reflecting adaptation to the formation's meandering, sediment-laden waterways.

Ornithischian Dinosaurs

The Elrhaz Formation has yielded remains of several ornithischian dinosaurs, primarily basal and iguanodontian ornithopods adapted to the floodplain environment of what is now . These herbivores represent a diverse array of body plans, from small bipedal grazers to larger, more robust forms capable of processing tougher plant material. Fossils, including partial skeletons and isolated bones, indicate that ornithischians were common members of the local , contributing to the ecological dynamics of the riverine habitats. Elrhazosaurus nigeriensis, a basal ornithischian known from fragmentary postcranial remains such as a and ilium discovered in the Gadoufaoua region, is interpreted as a small, bipedal grazer approximately 2 meters long. Erected as a distinct based on differences in femoral morphology from related taxa like Valdosaurus, it exhibits features typical of early neornithischians, including a slender build suited for agile movement across open floodplains. Its limb proportions suggest a primarily terrestrial lifestyle, with adaptations for browsing low vegetation in a habitat dominated by seasonal watercourses. Lurdusaurus arenatus, an iguanodontian ornithopod represented by partial including skulls and limbs from multiple individuals, was a heavily built reaching up to 9 meters in length and weighing around 5 tons. Its robust , with particularly strong forelimbs featuring grasping hands and thumb spikes, indicates a capability for pulling down branches or manipulating vegetation, distinguishing it from more gracile relatives. The elongated neck and heavy torso suggest a semi-aquatic or grounded strategy in the sandy, river-dominated of the formation. Ouranosaurus nigeriensis, another iguanodontian, is known from nearly complete skeletons, including iconic specimens with preserved dorsal s formed by elongated neural spines up to 2 meters tall. Measuring 7-8 meters long, this bipedal-to-quadrupedal form had a broad duck-like and battery of leaf-shaped teeth with median ridges, enabling efficient shearing of fibrous plants. The structure is hypothesized to have aided in the hot, arid climate punctuated by wet seasons, potentially increasing surface area for heat exchange or display purposes. Dietary inferences for these ornithischians derive from dental patterns and tooth morphology, revealing adaptations to the tough, such as ferns, cycads, and prevalent in the Aptian-Albian paleoenvironment. Elrhazosaurus likely grazed on softer ground cover, while and processed more abrasive, woody material through heavy occlusal on their ridged teeth, facilitating nutrient extraction from resilient in a resource-variable . These ornithischians coexisted with sauropods in mixed feeding guilds, partitioning access to the available plant resources along river margins.

Theropod Dinosaurs

The of has yielded a diverse assemblage of theropod dinosaurs from the (Aptian-Albian stages, approximately 112 million years ago), representing multiple clades including abelisauroids, carcharodontosaurids, and spinosaurids. These carnivorous bipedal predators occupied varied ecological niches in a fluvial paleoenvironment characterized by rivers and floodplains, with suggesting adaptations for both terrestrial and semi-aquatic . The theropod fauna highlights the biogeographic importance of during this period, contributing to understanding the radiation of large-bodied predators in . Among the smaller theropods, Afromimus tenerensis is a basal abelisauroid, likely affiliated with , known from a fragmentary including vertebrae, limb bones, and a pedal ungual discovered in the Gadoufaoua locality. This agile predator, estimated at 2-3 meters in length, featured slender limb elements and a gracile build suited for swift terrestrial pursuit, contrasting with the more robust forms in the assemblage. Initially classified as an ornithomimosaur, subsequent phylogenetic analyses repositioned it within Abelisauroidea based on shared features like the morphology of the astragalus and pedal phalanges. Larger predators include Eocarcharia dinops, a basal carcharodontosaurid represented by cranial elements such as a and postorbital from the same locality, indicating a body length of 6-8 meters. Its robust featured an enlarged promaxillary and a prominent orbital boss on the postorbital, suggesting adaptations for powerful biting and possibly intraspecific combat via head-butting, with tall, laterally compressed teeth ideal for slicing flesh. Similarly, Kryptops palaios, a basal abelisauroid, is known from a partial including a , vertebrae, and pelvic girdle, with an estimated length of 6-7 meters and a distinctive vaulted formed by a deep secondary wall in the antorbital fossa. The 's textured external surface implies a keratinous covering, and its broad, low profile points to a strong for subduing prey. Spinosaurid diversity is particularly notable, exemplified by tenerensis and lapparenti, both piscivorous forms with elongated, crocodile-like snouts adapted for catching in riverine settings. tenerensis, described from a nearly complete including a partial , reached lengths of up to 11 meters and weighed around 5 tons, featuring conical teeth with fine serrations, robust forelimbs with enlarged manual claws, and elongated neural spines forming a low dorsal sail. lapparenti, based on fragmentary jaw and vertebral material from Gadoufaoua, shares similar longirostrine morphology but is smaller, potentially around 5-6 meters; taxonomic debate persists, with some analyses proposing it as a junior synonym of due to overlapping diagnostic traits like the premaxillary rosette structure. Evidence for semi-aquatic lifestyles among Elrhaz spinosaurids derives from oxygen isotope analyses of , revealing δ¹⁸O values more negative than those of co-occurring terrestrial theropods, indicating substantial time spent in aquatic environments similar to modern crocodilians. This in Suchomimus suggests a primarily piscivorous diet, with occasional predation on crocodyliforms or smaller vertebrates, facilitating niche partitioning from terrestrial hunters like carcharodontosaurids. Dense microstructure and conical further support wading or shallow-water foraging in the formation's river systems.

Sauropod Dinosaurs

The Elrhaz Formation of has yielded remains of a single sauropod taxon, the rebbachisaurid Nigersaurus taqueti, representing one of the most abundant large herbivores in this ecosystem. First discovered in the 1950s by French paleontologist Philippe Taquet during expeditions to the Gadoufaoua region, initial bones were not fully identified until Paul Sereno's team collected more complete material in 1997, leading to the formal naming in 1999 and detailed description in 2007. This medium-sized sauropod, reaching lengths of about 9 meters and weighing around 4 tons, is distinguished by its highly specialized cranial anatomy adapted for ground-level herbivory. Nigersaurus taqueti possessed an extraordinarily lightweight skull, comprising less than 1% of its body mass, with large fenestrae and thin bones that minimized weight while supporting a wide, straight-edged muzzle. Its most striking feature was a dental battery containing over 500 replaceable, needle-like teeth arranged in multiple rows along the jaws, functioning like a to sweep and slice soft vegetation such as ferns and horsetails from settings. These teeth, which were continuously replaced at a rate far exceeding that of other sauropods, allowed for efficient low browsing close to the ground, with the head held in a near-horizontal position due to robust neck vertebrae and limited mobility. This feeding strategy represents an extreme specialization within diplodocoid sauropods, enabling Nigersaurus to exploit low-lying plants unavailable to taller browsers. Fossil evidence includes multiple partial skeletons from both juvenile and adult individuals, recovered from fluvial sandstones of the Elrhaz Formation, suggesting gregarious and possible structures among this species. As an early representative of Rebbachisauridae in the Aptian-Albian stages (approximately 115–105 million years ago), highlights the diversification of this clade in northern during the breakup of , providing key insights into the biogeographic distribution of sauropods across the continent.

References

  1. https://nigerlex.geolex.org/formations/Elrhaz%20Fm
  2. https://www.app.pan.pl/archive/published/app53/app53-015.pdf
  3. http://faculty.washington.edu/gpwilson/Reprints/Sereno_etal_1998.pdf
  4. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0001230
  5. https://doi.org/10.47909/978-9916-9760-6-7
  6. https://www.researchgate.net/publication/284617900_Between_Tendaguru_and_Bahariya_on_the_age_of_the_Early_Cretaceous_dinosaur_sites_from_the_Continental_Intercalaire_and_other_African_formations
  7. https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/comptes-rendus-palevol2022v21a41.pdf
  8. https://bioone.org/journals/acta-palaeontologica-polonica/volume-53/issue-1/app.2008.0102/Basal-Abelisaurid-and-Carcharodontosaurid-Theropods-from-the-Lower-Cretaceous-Elrhaz/10.4202/app.2008.0102.full
  9. https://www.nigerheritage.org/dinosaurs
  10. https://naturalhistory.si.edu/sites/default/files/media/translated_publications/Taquet_76.pdf
  11. https://doc.rero.ch/record/14477/files/PAL_E1671.pdf
  12. https://education.nationalgeographic.org/resource/adventure-science/
  13. https://www.researchgate.net/publication/275485132_Arrested_Heritage_The_Politics_of_Inscription_into_the_UNESCO_World_Heritage_List_The_Case_of_Agadez_in_Niger
  14. https://www.academia.edu/85477578/Stratigraphic_Lexicon_The_Sedimentary_Formations_of_The_Republic_of_Niger_Africa
  15. https://pubs.geoscienceworld.org/sgf/bsgf/article/S5-XIX/4-6/493/516952/Stratigraphie-et-identification-des-formations
  16. https://www.researchgate.net/publication/366019585_Microvertebrate_fauna_from_Gadoufaoua_Niger_Aptian_Early_Cretaceous
  17. https://www.science.org/cms/asset/1356cdf9-cf33-41f3-9ecd-d082521bf652/pap.pdf
  18. https://www.aljazeera.com/features/2025/9/12/dinosaurs-to-supercrocs-nigers-bone-keepers-preserve-its-ancient-fossils
  19. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144695
  20. https://www.naturalhistory.si.edu/sites/default/files/media/translated_publications/Taquet%25252070.pdf
  21. https://doi.org/10.5852/cr-palevol2022v21a41
  22. https://zookeys.pensoft.net/article/47517/
  23. https://hal.science/hal-01796276/document
  24. https://pfeil-verlag.de/wp-content/uploads/2015/05/2_48d07.pdf
  25. https://doi.org/10.1016/j.cretres.2019.06.003
  26. https://doi.org/10.1016/j.crpv.2018.04.004
  27. https://sciencepress.mnhn.fr/sites/default/files/articles/hd/comptes-rendus-palevol2022v21a41-pdfa.pdf
  28. https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=67329
  29. https://www.researchgate.net/publication/278720021_A_New_Long-Necked_Turtle_Laganemys_tenerensis_Pleurodira_Araripemydidae_from_the_Elrhaz_Formation_Aptian-Albian_of_Niger
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC7188693/
  31. https://paulsereno.uchicago.edu/discoveries/anatosuchus_minor/
  32. https://www.researchgate.net/publication/272811387_Cretaceous_Crocodyliforms_from_the_Sahara
  33. https://paulsereno.uchicago.edu/discoveries/araripesuchus_wegeneri/
  34. https://www.researchgate.net/publication/11672584_The_Giant_Crocodyliform_Sarcosuchus_from_the_Cretaceous_of_Africa
  35. https://www.researchgate.net/publication/285683839_A_new_Early_Cretaceous_crocodyliform_from_Niger
  36. https://pmc.ncbi.nlm.nih.gov/articles/PMC8511751/
  37. https://www.researchgate.net/profile/Peter-Galton/publication/279756086_Notes_on_Neocomian_Lower_Cretaceous_ornithopod_dinosaurs_from_England_-_Hypsilophodon_Valdosaurus_Camptosaurus_Iguanodon_-_and_referred_specimens_from_Romania_and_elsewhere/links/004635386a60b63dd3000000/Notes-on-Neocomian-Lower-Cretaceous-ornithopod-dinosaurs-from-England-Hypsilophodon-Valdosaurus-Camptosaurus-Iguanodon-and-referred-specimens-from-Romania-and-elsewhere.pdf
  38. https://www.sciencedirect.com/science/article/abs/pii/S0753396999800093
  39. https://www.sciencedirect.com/science/article/abs/pii/S1464343X19302250
  40. https://www.sciencedirect.com/science/article/abs/pii/S1251805098800542
Add your contribution
Related Hubs
User Avatar
No comments yet.