Sigilmassasaurus brevicollis, Russell, 1996

Mauro, Lacerda, Isasmendi, Erik, Delcourt, Rafael, Marcelo, Fernandes, John & Hutchinson, 2024, New theropod dinosaur remains from the ºpper Cretaceous of the Kem Kem Group (Eastern Morocco) clarify spinosaurid morphology, Zoological Journal of the Linnean Society 202 : -

Sigilmassasaurus brevicollis

( Fig. 13)

Referred specimen

A completely preserved posterior cervical vertebra (NHMºK PV R 38358)*

Morphological description

NHMºK PV R 38358 is an almost complete cervical vertebra, with only part of the neural spine missing* Based on the axial sequence proposed by Evers et al. (2015), NHMºK PV R 38358 can be identified as a C9 (Fig* 13)*

Ŋe vertebral centrum is c * 125 mm long anteroposteriorly, c * 140 mm wide, and c * 95 mm high* It is strongly opisthocoelous and the anterior articular surface is surrounded by a rim (Fig* 13A, B)* NHMºK PV R 38358 has a vertebral centrum that is shorter than it is wide, being 12% wider than it is long, and its dorsal surface is slightly anteroposteriorly shorter than ventral surface* Ŋe articular facets are wide, with the anterior and the posterior articular surfaces being 1*4 and 1*6 times wider than they are tall, respectively (Fig* 13)* Ŋe anterior articular surface is strongly convex and the posterior one is strongly concave* In anterior view, the anterior articular surface is pronouncedly elliptical (Fig* 13A, B) and, in posterior view, the posterior one has a reniform outline (Fig* 13C, D)* Ŋe ventral surface exhibits a well-developed ventral keel that extends to the anterior and posterior margins of the vertebral centrum, widening slightly transversely towards these edges (Fig* 13G, H)* In lateral view, the anterior and posterior parts of the keel project further ventrally, so that it is concave at midlength of the centrum (Fig* 13I–L)* Anteriorly, the ventral keel gradually becomes lower and merges into a small, rough, triangular area located immediately anterior to the parapophyses (Fig* 13G, H)* Lateral to the ventral keel, a fossa is present on each side of the centrum* Ŋese fossae are delimited anterolaterally by the parapophyses and the lamina that connects the parapophyses to a small anterior triangular area, and posterolaterally by a lamina that extends from the parapophyses posteriorly to the posterior articular facet (Fig* 13G–L)* No hypapophysis seems to be present in NHMºK PV R 38358*

Ŋe parapophyses are robust, ‘buưon-shaped’ structures that are long and project ventrolaterally; located anteroventrally on the lateral surfaces of the centrum (Fig* 13A–D, G–L)* Ŋe articular surfaces of the parapophyses are concave and oval in outline* From the posterior margin of each of the parapophyses, a rounded ridge extends posteriorly; these are the ridges that laterally delimit the ventral fossae (Fig* 13G, H)* Above the parapophyses, a single and large central pneumatic foramen is present on each side of the NHMºK PV R 38358 vertebral centrum and it penetrates the bone anteroventrally (Fig* 13I–L)* Each foramen has a different shape: the right one is triangular and anteroposteriorly larger than tall (Fig* 13), whereas the less is oval and taller than its length anteroposteriorly (Fig* 13K, L)*

Ŋe neurocentral suture in NHMºK PV R 38358 is still visible* Ŋe neural canal is large, subrectangular to oval in shape, and transversely wider than tall (Fig* 13A–D)* Ŋe pleurocentral depressions are located ventral to this suture, anterodorsally located on the centrum*

Ŋe transverse processes are very large and project ventrolaterally at an angle of c * 40° to the lateral surface (Fig* 13A–D)* In anterior view, the transverse processes are quite straight dorsoventrally (their dorsal surfaces are distinctly flat), but towards the diapophyses they curve slightly more ventrally* In dorsal view, the posterior surfaces of the transverse processes are straight and laterally directed (Fig* 13E, F)* Ŋe anterior margin is gently concave in dorsal view and expands anteriorly near the diapophyses* Ŋe diapophyses face ventrolaterally and are convex and triangular in outline* Both prezygodiapophyseal and postzygodiapophyseal laminae are present* Ŋese laminae are robust, rounded, developed in a similar way, and are less marked near the diapophysis* Ŋe prezygodiapophyseal lamina extends laterally from the anterolateral margin of the prezygapophyses along the anterodorsal margin of the transverse process, reaching the anterodorsal margin of the diapophyses* Ŋe postzygodiapophyseal lamina runs from the anterolateral margin of the postzygapophyses toward the diapophyses, forming the posterodorsal edge of the transverse process* Ŋe centroprezygapophyseal lamina is directed anterolaterally and merges with the prezygodiapophyseal lamina on the anterior surface of the base of the prezygapophyses, with the lamina being less marked, but more robust and rounded than the prezygodiapophyseal lamina*

Ŋe centrodiapophyseal lamina is present on the ventral surface of the transverse process* Ŋis is very prominent and it seems not to be bifurcated into the anterior centrodiapophyseal and posterior centrodiapophyseal laminae* However, there is another lamina that runs from the ventral surface of the transverse process toward the posterodorsal margin of the centrum [probably the posterior centrodiapophyseal lamina according to Evers et al. (2015)]* Ŋe centrodiapophyseal lamina runs from the diapophysis, extending from the ventral surface of the transverse process toward the lateral side of the centrum, resulting in a ‘T-shaped’ cross-section of the transverse process*

Regarding the pneumaticity of the vertebra, the prezygocentrodiapophyseal fossa is open ventrolaterally and extends throughout the anteroventral part of the transverse process (Fig*13A,B)*Ŋisfossaisdelimitedbythecentroprezygapophyseal lamina anteriorly, the centrodiapophyseal lamina posteriorly, and the prezygodiapophyseal lamina dorsally* Ŋe prezygocentrodiapophyseal fossa presents a ‘slit-shaped’ foramen, quite high, narrow, and oval, which penetrates the pedicle of the prezygapophysis* Ŋe postzygocentrodiapophyseal fossa is located on the posterior surface of the transverse process, being larger than the prezygocentrodiapophyseal fossa (Fig* 13C, D)* Ŋis fossa is delimited anteriorly by the centrodiapophyseal lamina, posteriorly by the centropostzygapophyseal lamina and dorsally by the postzygodiapophyseal lamina* Moreover, it exhibits another pneumatic foramen, which penetrates posterolaterally into the transverse process, and is also more circular than that of the prezygocentrodiapophyseal fossa (Fig* 13C, D)*

Ŋe prezygapophyses are large and considerably separated, projecting more laterally than the vertebral centrum itself, being projected mainly dorsolaterally and slightly anteriorly (Fig* 13A–F)* Ŋe prezygapophyses are located dorsal to the transverse process in the anterior half of the transverse processes and their anterior margin is placed slightly anterior to the anterior margin of the transverse process (Fig* 13I–L)* Ŋe prezygapophyseal articular facets of the prezygapophyses are oval to subcircular in dorsal view, being wider lateromedially* Ŋey are dorsomedially facing, with an angle of 125° between both facets* Ŋese facets are slightly convex but almost flat, and slightly posteriorly inclined* Ŋere is no intraprezygapophyseal lamina between the prezygapophyses*

Ŋe postzygapophyses are also large, but more compact compared to the prezygapophyses and without an epipophysis* Ŋey extend posterodorsally beyond the posterior margin of the centrum, with half of the postzygapophyses posterior to the posterior margin of the centrum (Fig* 13I–L)* Ŋe postzygapophyseal facets are concave, with an inverted ‘teardropshape’, posteroventrally facing, and laterally oriented* Ŋey are connected anteromedially by the spinopostzygapophyseal laminae, but they are not connected ventromedially because there is no intrapostzygapophyseal lamina* Nevertheless, from the posteromedial margin of the postzygapophyses, two narrow spinopostzygapophyseal laminae extend ventrally, reaching the dorsolateraledgeoftheneuralspine*Ŋespinopostzygapophyseal laminae are well developed, robust, and rounded, being delimited dorsolaterally by the spinopostzygapophyseal fossa, which is quite triangular and open ventrally* Ŋis fossa is laterally delimited by postzygapophyses and ventromedially oriented laminae*

Ŋe neural spine is not completely preserved, but its base suggests that it was a ‘spike-like’ process that projected posterodorsally (Fig* 13A–F)* Ŋe cross-section of its base is subcircular in dorsal view, and is connected to the prezygapophyses by the spinoprezygapophyseal laminae* Ŋese laminae are poorly developed in comparison to the other laminae present in the vertebra; besides that, they are rounded and extend from the anterior surface of the neural spine to the posteromedial margin of the prezygapophyses, forming an inverted ‘V-shaped’ structure (Fig* 13A–F)* A prespinal lamina (sensu Evers et al. 2015) is also present on the anterior surface of the neural arch, situated between the spinoprezygapophyseal laminae* Ŋis lamina is low, dorsoventrally oriented, and projects slightly ventrally into the neural canal* Ŋis lamina, together with the spinoprezygapophyseal laminae, delimits a shallow triangular depression on the anterior surface of the neural arch*

Morphological comparisons

Specimen NHMºK PV R 38358 shares with many earlybranching tetanuran theropods the single pneumatic foramen on the lateral surface of the vertebral centrum ( Carrano et al. 2012)* Furthermore, this posterior cervical vertebra shares with Megalosauroidea taxa the bordered (or rimmed) anterior articular surface of the centrum ( Carrano et al. 2012, Evers et al. 2015, Malafaia et al. 2020, Barker et al. 2021)* However, this trait may be also present in Allosaurus ( Rauhut and Pol 2019) * In the specimen studied here, the parapophyses are enlarged and exhibit a strongly concave facet, similar with the spinosaurids Baryonyx , Ichthyovenator , Sigilmassasaurus , and Suchomimus ( Allain et al. 2012, Evers et al. 2015)* Another feature shared between NHMºK PV R 38358 and spinosaurids is the presence of a ventral keel on the vertebral centrum, with the anterior end projecting anteriorly (a synapomorphy for Spinosauridae — Schade et al. 2023)* Ŋe neural arch of NHMºK PV R 38358 lacks epipophyses, similar to the posterior cervicals of Baryonyx [considering the arrangement proposed by Evers et al. (2015)], and Sigilmassasaurus ( Russell 1996, McFeeters et al. 2013, Evers et al. 2015)* Ŋe neural spine is inferred to be ‘spike-like’ in NHMºK PV R 38358, a feature also shared with Baryonyx and Sigilmassasaurus ( Evers et al. 2015) *

Ŋe vertebral centrum of NHMºK PV R 38358 is very wide, with the anterior articular surface being 1*4 times wider than it is tall, similar to the condition observed in Ichthyovenator and Sigilmassasaurus , in the laưer being more than 1*5 times larger than high ( Russell 1996, McFeeters et al. 2013, Evers et al. 2015)* Specimen NHMºK PV R 38358 also shares with Ichthyovenator and Sigilmassasaurus the lack of intraprezygapophyseal and intrapostzygapophyseal laminae ( Allain et al. 2012, Evers et al. 2015)* Ŋe posterior cervical vertebra (C9) studied here further resembles the posterior cervicals of Sigilmassasaurus brevicollis by having large, transverse processes that exhibit pneumatic foramina deep beneath their base ( McFeeters et al. 2013, Evers et al. 2015)*

If the emended diagnosis of Sigilmassasaurus brevicollis proposed by Evers et al. (2015) is considered, specimen NHMºK PV R 38358 shares with the former the reduced lamination of the neural arch with the centrodiapophyseal laminae not being divided into anterior and posterior centrodiapophyseal laminae [autapomorphy proposed by Evers et al. (2015)]* Nevertheless, the specimen described here lacks the anterior tubercle that is present on the anterior articular surfaces of the posterior cervical and anterior dorsal vertebrae of Sigilmassasaurus brevicollis ( McFeeters et al. 2013, Evers et al. 2015), but this feature is more subtle in the BSPG 2011 I 115 cervical vertebra ( Evers et al. 2015) and also absent in ROM 65537 ( McFeeters et al. 2013)* Ŋe posterior vertebra NHMºK PV R 38358 can be safely assigned to Spinosauridae , furthermore, due to the above-mentioned features shared with Sigilmassasaurus brevicollis , we here assign this specimen to the same taxon*

Allosauroidea Marsh, 1878

Carcharodontosauria Benson et al., 2010

Carcharodontosauridae Stromer, 1931

Carcharodontosauridae gen. et sp. indet.

( Fig. 14)

Referred specimen

A partial less ischium (NHMºK PV R 16437)*

Morphological description

Ŋe less ischium NHMºK PV R 16437 has its proximal portion preserved, missing the distalmost portion of the shass and the ventralmost portion of the obturator process (Fig* 14)* Ŋe iliac and pubic peduncles are separated by a concave acetabular rim that is shallow, wide in anterior view with a middle constriction, giving it an ‘hourglass-shape’ in proximal view (Fig* 14)* Ŋe peduncles are subequal in size* In the proximal region, the iliac articular surface is triangular and deeply concave suggesting a peg-and-socket articulation (Fig* 14)* In the anteriormost region of the iliac peduncle, anterior to the articular surface with the ilium, the ischium is thick mediolaterally, forming the ischial antitrochanter, which is parallelogram-shaped in anterior view* Although the antitrochanter is thick, it is not well projected, being a reduced ridge* In the posterior part of the iliac joint, there is a posterior flange that rises, and it is broken in the dorsalmost portion* Ŋe pubic peduncle is subtriangular and medially concave with the articular surface being laterally oriented*

Ŋe lateral and medial surfaces of the ischium are concave between the peduncles, with the concavity displaced dorsally in the lateral side and ventrally in the medial side* Posteroventral to the flange in the iliac peduncle, a deep and rugose sulcus, homologous to the ischial tuberosity (e*g* Hutchinson 2001b, Brusaưe et al. 2008, Cuesta et al. 2018), runs in the lateral surface becoming shallower posteriorly (Fig* 14)* Ŋe most proximal part of this sulcus, somewhat elliptical in shape, represents the osteological correlate of the origin of the muscle flexor tibialis internus 3 (FTI3), which is delimited slightly more distally* Ŋe most distal part of the sulcus in the posterodorsal region of the ischial shass, which is more linear, less elliptical than the proximal part, becomes shallower distally, and represents the osteological correlate of the origin of the muscle adductor femoris 2 (ADD2) (Fig* 14A, B)* Both of these muscle origins are level II inferences by Witmer’s (1995) systematization and are topologically compatible with other theropods (e*g* ceratosaurs— Cerroni et al. 2024, early tetanurans— Lacerda et al. 2024, and derived coelurosaurs— Carrano and Hutchinson 2002)*

In the preserved portion of the ischium, the shass is dorsoventrally flaưened, giving it a subrectangular shape, lacking the distalmost part (Fig* 14)* Ventral to the shass and posterior to the pubic peduncle, the obturator process is separated from the pubic peduncle by a shallow and anteroposteriorly notch* Posterior to this notch, the obturator process is twisted medially from the pubic peduncle and broken in its ventralmost portion (however, a notch ventral to obturator process can be noted) and seems to be confluent with the shass (Fig* 14)* Although the ischial shass is not completely preserved, the preserved part is straight, suggesting that the orientation of the main axis of the ischium was straight in NHMºK PV R 16437*

Morphological comparisons

Ŋe overall shape of the NHMºK PV R 16437 partial ischium resembles that of carcharodontosaurid theropods rather than of other dinosaurs* Ŋe acetabular rim is shallow in lateral view with a weak ‘º-shape’ due to the ventral position of the pubic peduncle, as seen in allosauroids (sensu Rauhut and Pol 2019), including the carcharodontosaurids Acrocanthosaurus , Concavenator , Giganotosaurus , Mapusaurus , and Neovenator * In some neovenatorids, such as Siats , the acetabular rim is shallow, not forming a ‘º-shaped’ border, being straighter than in other allosauroids ( Zanno and Makovicky 2013)* Ŋe ‘º-shape’ of the acetabular rim is more pronounced in megalosauroids such as Piatnitzkysaurus and also in the spinosaurids Baryonyx , Ichthyovenator , Vallibonavenatrix, FSAC-KK 11888, and possibly in Suchomimus due to a dorsal projection of the pubic peduncle ( Allain et al. 2012, Malafaia et al. 2020, Sereno et al. 2022, Lacerda et al. 2024)* Ŋis condition differs from that observed in NHMºK PV R 16437*

Ŋe ilioischiatic articulation of NHMºK PV R 16437 has a deep peg-and-socket (or ball-and-socket) configuration, as seen in Acrocanthosaurus , Concavenator , Giganotosaurus , Mapusaurus , and Siats ( Stovall and Langston 1950, Coria and Currie 2006, Carrano et al. 2012, Zanno and Makovicky 2013, Cuesta et al. 2018, Rauhut and Pol 2019, Lacerda et al. 2023)* In other theropods, this articulation has a concave plane configuration (e*g* Carrano et al. 2012, Lacerda et al. 2023, Isasmendi et al. 2024)*

Ŋe ischial antitrochanter is a well-developed, notch-shaped structure in coelophysoids, some ceratosaurs, the early tetanuran Sinosaurus , the spinosaurid Ichthyovenator , and the neovenatorid Siats ; it is a reduced notch in the ischium of other theropods (e*g* Allain et al. 2012, Carrano et al. 2012, Zanno and Makovicky 2013, Cuesta et al. 2018, Lacerda et al. 2023)* In NHMºK PV R 16437, although the ischial antitrochanter is a reduced ridge, it represents a thick structure at its base, and this is more comparable with forms such as Acrocanthosaurus , Giganotosaurus , and Sinraptor , than Siats and other contemporary theropods such as spinosaurids*

Ŋe presence of the sulcus in the dorsolateral shass of the ischium, which is posterior to the flange, is similar in NHMºK PV R 16437 and other theropods (e*g* Zanno and Makovicky 2013, Cuesta et al. 2018); however, in the ischium described here it is deeper, similar to carcharodontosaurids and neovenatorids rather than spinosaurids* Consequently, the osteological correlates of the origins of the muscles FTI3 (proximal) and ADD2 (distal) in NHMºK PV R 16437 are deeper than those noted in other non-carcharodontosaurid theropods (e*g* Carrano and Hutchinson 2002, Cerroni et al. 2024, Lacerda et al. 2024)*

Ŋe obturator process of NHMºK PV R 16437 presents a notch that is shared with other theropods such as the ceratosaur Ceratosaurus , piatnitzkysaurids, spinosaurids (except Ichthyovenator ), and allosauroids such as Acrocanthosaurus, Allosaurus , Giganotosaurus , and Sinraptor ( Stovall and Langston 1950, Carrano et al. 2012, Lacerda et al. 2023)* However, NHMºK PV R 16437 has a lamina, part of the dorsalmost portion of the obturator process, which is immediately ventral to the pubic peduncle* Ŋis feature is also shared with the metriacanthosaurid Sinraptor and the carcharodontosaurid Giganotosaurus *

Furthermore, if the ischial shass in NHMºK PV R 16437 is indeed straight, as the preserved portion suggests, this would be another feature shared between this individual and carcharodontosaurids (also seem in some allosauroids— Madsen 1976), but not with some early diverging tetanurans and also metriacanthosaurids* Ŋus, based on the set of characteristics shared between NHMºK PV R 16437 and carcharodontosaurid theropods, as well as the differences between this ischium and those of spinosaurids, we assign this material to an indeterminate Carcharodontosauridae *

Brief survey of theropod dinosaurs from the Kem Kem Group

Several records of theropod dinosaurs are known from the North Africa, especially those that derive from Middle Cretaceous rocks from the Kem Kem Group region, therefore, suggesting a high theropod diversity* However, much of the diversity known for the region is represented by shed teeth, which are more likely to be fossilized as they are more resistant to weathering and taphonomic alterations ( Benyoucef et al. 2015, Hendrickx et al. 2024)* Ŋere is also a good and broad ichnological record that helps confirm faunal occurrences and serves as a proxy for more reliable palaeoenvironmental reconstructions ( Belvedere et al. 2013, Ibrahim et al. 2014b)* Regarding skeletal remains, records are scarcer ( Hendrickx et al. 2024); however, they are still of broad relevance for understanding both biogeographical and evolutionary issues in different clades* Below, a brief nonexhaustive survey of the body fossil occurrences is presented, as well as integration with our findings and their relevance to current knowledge*

Abelisauridae

Ŋe fossil record of abelisaurids is one of the most abundant in the Kem Kem Group, being less abundant only than spinosaurids* Russell (1996) described several bone fragments, including two partial right dentaries, in addition to two partial cervical vertebrae that were aưributed to an undetermined theropod, but recently were assigned to abelisaurids ( Souza-Júnior et al. 2023)* Although the locality from which these materials were derived is unknown, they were probably recovered from the Cenomanian of southern Morocco ( Souza-Júnior et al. 2023)* A partially preserved maxilla that probably comes from Erfoud was described by Mahler (2005) * Novas et al. (2005) related a ungual pedal to Abelisauroidea from the Tafilalt region* A partially preserved less maxilla that derives from a region near Taouz was described by Porcheưi et al. (2011) * Ŋe proximal part of a femur was described by Chiarenza and Cau (2016) * In addition to these, an axis vertebra described by Smyth et al. (2020a) was also aưributed to Abelisauridae *

Noasauridae

A postcranial skeleton that is relatively well preserved, including hindlimbs and partial forelimbs as well as part of the tail, was erected as Deltradomeus agilis by Sereno et al. (1996) * However, the assignment of this taxon to noasaurid theropods occurred only in later phylogenetic analyses (e*g* Sereno et al. 2004) and the phylogenetic position of this taxon remains under debate* Evans et al. (2015) described a well-preserved femur from south-east Taouz, which could possibly belong to Deltradomeus * Another noasaurid occurrence was presented by Smyth et al. (2020a), based on an isolated cervical vertebra*

Spinosauridae

Ŋis group is one of the most representative in the Kem Kem Group fossil record; however, the nature of the material is isolated or semi-articulated fossils* Two partial dentaries from south-eastern Morocco were described by Buffetaut (1989), being both referred to Spinosaurus cf* Sp * aegyptiacus * Based on a set of isolated bones, including cervical vertebrae, dorsal neural arch, and a fragmentary dentary recovered from Morocco, Russell (1996) erected the name Spinosaurus maroccanus ; later on, Taquet and Russell (1998) referred a rostrum and some axial elements recovered from the Algerian portion of the Sahara Desert to this species* However, this species is frequently regarded as a nomen dubium (e*g* Carrano et al. 2012), a junior synonym of Spinosaurus aegyptiacus (e*g* Ibrahim et al. 2014a), or Spinosaurinae indet* (e*g* Lacerda et al. 2022)* Milner (2003) presented a rostrum and a relatively well-preserved dentary from Morocco in a brief note; both of them were referred to Sp * aegyptiacus * Ŋis rostrum is redescribed in detail in this work (NHMºK PV R 16420) and considered as an indeterminate Spinosaurinae , agreeing with the current debate (e*g* Sales and Schultz 2017, Lacerda et al. 2022)* Another rostrum, which represents the most complete and well-preserved known to date, and a pair of nasals from Morocco were described by Dal Sasso et al. (2005), with both referred to Spinosauru s cf* Sp * aegyptiacus * Lately, some studies (e*g* Sales and Schultz 2017, Lakin and Longrich 2019, Lacerda et al. 2022) have argued that the most reliable identification of that rostrum is Spinosaurinae indet* due to a lack of overlap between these specimens and the Sp * aegyptiacus holotype * Based on several skeletal elements of a subadult individual, Ibrahim et al. (2014a) proposed a neotype to Sp * aegyptiacus , and later on, new skeletal remains possibly of the same individual represented by a robust tail were also recovered from Morocco ( Ibrahim et al. 2020a)* Two morphotypes of spinosaurids, Sp * aegyptiacus and cf* Sigilmassasaurus brevicollis , were identified by Hendrickx et al. (2016) based on six quadrates that probably derived from Morocco * A tiny pedal ungual recovered from between the villages of Taouz and Begaa was presented by Maganuco and Dal Sasso (2018) * Arden et al. (2019) also described two morphotypes of spinosaurids from the Kem Kem Group: one referred to Sp * cf* Sp * aegyptiacus based on frontals and a frontoparietal, and a skull roof referred to Sigilmassasaurus cf* Si * brevicollis * Based on cranial remains and isolated axial elements, Lakin and Longrich (2019) also described fossils referred to Si * brevicollis and Sp * cf* Sp * aegyptiacus * Besides the previous mentions, other studies also described axial elements of Sigilmassasaurus brevicollis recovered from the same region (e*g* Russell 1996, McFeeters et al. 2013, Evers et al. 2015)*

In this contribution we have described several specimens that expand the knowledge of occurrences of spinosaurids in the Kem Kem Group* Among these, we have presented a cervical vertebra referred to Si * brevicollis (NHMºK PV R 38358), in addition to nine specimens (NHMºK PV R 16391, 16422, 16423, 16424, 16426, 16430, 16431, 16433, 16438) that we conservatively classified as indeterminate Spinosaurinae * Our findings, combined with materials mentioned above, contribute to general aspects of the occurrence of spinosaurids in the region, making them one of the most abundant groups of theropod dinosaurs in the Kem Kem Group*

Carcharodontosauridae

At least two species are known from the Kem Kem Group (although some studies consider only one species— Ibrahim et al. 2020a)* A nearly complete skull and some vertebral elements of Carcharodontosaurus saharicus were described by Sereno et al. (1996), in which a neotype was designated, recovered from the Douira Formation, south-eastern Morocco ( Sereno et al. 1996, Ibrahim et al. 2020a)* An isolated and fragmentary portion of a dentary [originally referred to an abelisaurid by Russell (1996) —see Ibrahim et al. (2020a)] can also be assigned to C * saharicus * A second carcharodontosaurid species, Sauroniops pachytholus , was erected by Cau et al. (2013) based on an almost complete frontal* Later on, Paterna and Cau (2023) also referred additional materials (a partial maxilla and a jugal) to Carcharodontosauridae , discussing the status of both— Carcharodontosaurus and Sauroniops * A probably indeterminate carcharodontosaurids manual ungual [ Ibrahim et al. (2020a), originally described as Ŋeropoda indet* by Russell (1996)] adds to the fossil record of this clade*

Here we also provided the description of an isolated ischium we identify as an indeterminate carcharodontosaurid (NHMºK PV R 16437), adding to the fossil record of this clade from the Kem Kem Group*

Taxonomic ađributions of NHMUK PV R 16420 and MSNM V4047 snouts

Ŋere is a consensus in the literature considering both well-preserved rostra from the Kem Kem Group—NHMºK PV R 16420 and MSNM V4047—as Spinosaurinae theropods (e*g* Milner 2003, Dal Sasso et al. 2005, Lakin and Longrich 2019, Lacerda et al. 2022)* However, the referral of both to Spinosaurus aegyptiacus (e*g* Milner 2003, Dal Sasso et al. 2005, Ibrahim et al. 2014a) is not possible to corroborate, at least yet, due to the lack of overlap among these and the Sp * aegyptiacus holotype ( Evers et al. 2015, Sales and Schultz 2017, Lakin and Longrich 2019, Lacerda et al. 2022)*

Some studies ( Lakin and Longrich 2019, Lacerda et al. 2022) noted some differences between both specimens* Lakin and Longrich (2019) considered NHMºK PV R 16420 as having a deeply concave dorsal profile and a curved premaxillary ventral profile, a straighter maxillary tooth row, larger external nares, and distinct outline of the premaxilla when compared with MSNM V4047* Although Lakin and Longrich (2019) did not consider these, necessarily, as two distinct taxa, they considered this set of features enough to designate two distinct morphotypes* However, Lacerda et al. (2022) quantitatively showed a high degree of compression/erosion in NHMºK PV R 16420, preventing any morphological differentiation from MSNM V4047*

As previous noted, the only major differences between the two rostra are the number of premaxillary teeth and the paưern of the intramaxillary suture anteriorly* However, these features seem to have no systematic significance* Based on our detailed redescription, we reject the possibility of two distinct taxa based on the NHMºK PV R 16420 and MSNM V4047 rostra* Excluding some features that are taphonomic artefacts, both snouts have virtually the same shape and probably represent the same taxon*

One or two Spinosaurinae taxa in the Kem Kem Group?

Ŋere is a prolific debate regarding the presence of one or more spinosaurid species in the Cenomanian of the Kem Kem Group* Several studies consider that Spinosaurus aegyptiacus is the only well-established species from this region and Sigilmassasaurus brevicollis is not supported due to the lack of autapomorphies (e*g* Ibrahim et al. 2014a, 2020a, b, Maganuco and Dal Sasso 2018, Smyth et al. 2020b)* Meanwhile, other studies have argued the plausibility of two (contemporary?) species, considering Si * brevicollis a valid taxon ( McFeeters et al. 2013, Evers et al. 2015, Hendrickx et al. 2016, Hone and Holtz 2017, Arden et al. 2019)* However, there is a degree of plausibility to both propositions, as we explain here* On one hand, those studies that consider Sp * aegyptiacus the only species argue that any morphological variation noted in multiple specimens is due to ontogeny, individual variations or sexual dimorphism (e*g* Ibrahim et al. 2014b, Smyth et al. 2020b)* Nevertheless, there are no studies showing the main ontogenetic stages of Sp * aegyptiacus , for example, leaving these propositions as speculative* On the other hand, several ‘diagnostic’ or ‘autapomorphic’ features are described in the literature, and several studies discuss distinct morphotypes of spinosaurids from the Kem Kem Group (e*g* Chiarenza and Cau 2016, Hendrickx et al. 2016, Arden et al. 2019; McFeeters 2021)*

Ŋis study also supports different morphotypes from this geological unit, for example, based on the proximal portion of the femur described here (NHMºK PV R 16433) when compared with the proximal femur aưributed to Sp * aegyptiacus (FSAC-KK 11888; Ibrahim et al. 2014 a, Sereno et al. 2022)* Besides that, several fossil specimens that have been synonymized with, and referred to, Sp * aegyptiacus do not even overlap with the lost holotype specimen ( Evers et al. 2015, Sales and Schultz 2017, Lakin and Longrich 2019, Lacerda et al. 2022), and thus remain difficult to corroborate* Although this study does not intend to resolve these issues, we considered the extended diagnosis provided by Evers et al. (2015), and thus the potential validity of Si * brevicollis * Meanwhile, we did not relate other materials to Sp * aegyptiacus due to lack of overlap and the possibility of a proper morphological comparison* Our study highlights the complexity of the analysis of spinosaurid diversity from the Kem Kem Group, and describes some fossil remains in detail, instead of only mentioning the occurrences of fossils, lacking proper descriptions and anatomical comparisons* We urge a detailed review of all spinosaurid materials from the Kem Kem Group, and also suggest caution in considering either a single taxon of spinosaurine with a large amount of morphological variation, or two taxa lacking proper diagnosis; thus, encouraging more detailed/rigorous studies* Resolution of this issue probably depends upon new discoveries of specimens*