Megalosauridae (Fitzinger, 1843) sensu Benson, 2010

Malafaia, Elisabete, Mocho, Pedro, Escaso, Fernando, Narvaéz, Ivan & Ortega, Francisco, 2024, Taxonomic and stratigraphic update of the material historically attributed to Megalosaurus from Portugal, Acta Palaeontologica Polonica 69 (2), pp. 127-171 : 152-156

Megalosauridae indet.

Fig. 19 .

Previous identifications: The tooth crown (MNHN/UL.EPt.023) was attributed to Megalosaurus insignis by Lapparent and Zbyszewski (1957: 22).

Material. —One small tooth crown (MNHN/UL.EPt.023; Fig. 19 ) from Porto Dinheiro (Lourinhã, Portugal) and was possibly collected from upper Kimmeridgian–lowermost Tithonian levels of the Praia da Amoreira-Porto Novo Formation ( Fig. 2 ) ( Manuppella et al. 1999a).

Description. —MNHN/UL.EPt.023is represented by a relatively well-preserved small crown ( CH = 10.24 mm) of a lateral tooth, which preserves a fragment of the root. The crown is relatively low (CHR = 1.85) and highly compressed labiolingually (CBR = 0.54). It is triangular in lateral view and slightly recurved distally, with a convex mesial margin, a slightly concave distal margin, and an apex positioned beyond the level of the distal margin. The labial surface is convex, the lingual surface is flat, and the basal section is lanceolate shaped. Both mesial and distal margins are denticulated, straight and placed in the distal and mesial margins, respectively. The carinae have several small denticles that extend to the cervix in the distal carina, but they end at about the mid-height of the crown in the mesial carina. There are 22, 23, and 25 denticles per 5 mm in the apical, central, and basal sectors of the distal carina, respectively. The mesial carina is broken in the central and basal portions so only the apical denticles can be described. There are 28 denticles per 5 mm in the apical part of the mesial carina (see SOM 2). The distal denticles are subquadrangular in the apical part of the distal carina ( Fig. 19A 1 ) but become rectangular (slightly longer mesiodistally than the apicobasal wide) to the crown base ( Fig. 19A 7 ). They have convex external margins and are placed perpendicular to the carina. The mesial denticles are quadrangular and perpendicularly to the carina. Both mesial and distal denticles extend to the apex, forming a continuous serrated margin. The distal denticles become smaller to the base and the apex of the crown. A small flat surface adjacent to the distal carina is visible in the lingual surface. The enamel has an ornamentation formed by subtle ridges and crests oriented vertically (braided texture sensu Hendrickx et al. 2015a).

Remarks.—The results of the discriminant analysis classify MNHN/UL.EPt.023 as belonging to Dromaeosaurus (see Table 1). In the plot obtained by the LDA analysis it falls at the limit of the morphospace occupied by Raptorex , which has a great overlap with those of Dromaeosaurus and Deinonychus ( Fig. 16 ). This result may be related to the small size of the specimen and the high density of denticles in both carinae. However, in several dromaeosaurid taxa, the lateral teeth lack serrated carinae or, if present, the mesial carina has a characteristic twist, as occur in Dromaeosaurus ( Currie et al. 1990; Currie 1995; Hendrickx et al. 2015b). In addition, the lateral teeth of most dromaeosaurids have a wide apicobasally elongated concavity near the base of the labial surface ( Hendrickx et al. 2015b and references herein). The cladistic analysis of the dentition-based data matrix with constraints and including all studied morphotypes recovered the tooth crown (MNHN/ UL.EPt.023) in a polytomy within a poorly-resolved Megalosauroidea clade ( Fig. 18A ). The results of the analysis pruning a priori all the morphotypes from the Lusitanian Basin but MNHN/UL.EPt.023 found 7 MPTs (CI = 0.204, RI = 0.465, L = 1315). The consensus tree from these MPTs (CI = 0.203, RI = 0.462, L = 1320) recovered two clades within Megalosauroidea, a well-resolved Spinosauridae and a second group with megalosauridae taxa mostly placed in polytomy, also including MNHN/UL.EPt.023 ( Fig. 18C ). This specimen has a combination of features shared with lateral teeth of megalosaurids, including: (i) the braided and oriented texture of the enamel; (ii) the morphology of the distal denticles, which are subquadrangular to subrectangular, with short to well-developed interdenticular sulci and symmetrically convex external margins; (iii) the centrally positioned mesial and distal carinae on their mesial and distal surfaces, respectively; and (iv) a mesial carina not reaching the cervix. However, this specimen has a much higher denticles density in both mesial and distal carinae than is typical of megalosaurids. A higher number of denticles in the lateral teeth of juvenile individuals relative to that present in adult forms has been identified in some deeply nested theropod taxa (e.g., Mapusaurus, Canale et al. 2014 ), but the opposite pattern has been described for Coelophysis and Tyrannosaurus ( Long and McNamara 1997; Buckley and Currie 2014). Based on this combination of features and the results of the cladistic analysis, MNHN/UL.EPt.023 is interpreted here as a lateral tooth of a juvenile megalosaurid theropod and the relatively high density of denticles is proposed as been related with ontogeny. Moreover, based on its paleogeographic and stratigraphic distribution it may be related to Torvosaurus gurneyi .

Genus Torvosaurus Galton & Jensen, 1979

Type species: Torvosaurus tanneri Galton & Jensen, 1979 , from the late Kimmeridgian –early Tithonian Brushy Basin member of the Morrison Formation at Colorado, USA .

cf. Torvosaurus gurneyi Hendrickx & Mateus, 2014 Fig. 20 .

Previous identifications: MNHN/UL.EPt.8628 was described and figured by Lapparent and Zbyszewski (1957: 25, pl. 12: 17) and possibly corresponds to one of the first dinosaur remains identified in Portugal, which was mentioned by Carlos Ribeiro in 1863 ( Mateus 2005). This specimen is part of the material used to describe the putative new species Megalosaurus pombali . The fragment of tooth crown (MG 4813) was mentioned by Lapparent and Zbyszewski (1957) and assigned to Megalosaurus insignis ( Lapparent and Zbyszewski 1957: 22) . MG 4818 is labeled as Megalosaurus pombali , but we have not found any reference to this tooth fragment in previous publications.

Material. —Two tooth crown fragments (MG 4813, Fig. 20B ; MG 4818, Fig. 20C ) and a large mesial tooth (MNHN/ UL.EPt.8628, Fig. 20A ). MG 4813 was found in Montoito Lourinhã, Portugal), in Tithonian deposits of the Bombarral Formation ( Manuppella et al. 1999a). MG 4818 comes from Praia de S. Bernardino (Peniche, Portugal) from Kimmeridgian levels of the Alcobaça Formation ( Fürsich et al. 2021). MNHN/UL.EPt.8628 came from Porto Dinheiro (Lourinhã, Portugal) and was collected in upper Kimmeridgian–lowermost Tithonian levels of the Praia da Amoreira-Porto Novo

Formation ( Manuppella et al. 1999a). See Fig. 2 for the location of these specimens.

Description.—MNHN/UL.8628 corresponds to an almost complete tooth crown, without the apex, but with a fragment of the root preserved ( Fig. 20A ). It corresponds to a large lateral tooth (the preserved fragment is 75 mm in high). The crown is slightly compressed labiolingually ( CBR = 0.59), with a lanceolate basal section. Both lingual and labial surfaces are convex. In lateral view, the mesial surface is also convex, but the distal margin is mostly straight to slightly concave. The mesial and distal carinae are denticulated, but the mesial one is mostly worn, so is not possible to describe the morphology of the denticles. However, it is possible to verify that the mesial carina ends well above the base of the crown while the distal carina extends to the cervix. The distal carina is placed in the distal surface and is straight along the entire preserved length. There are 9 and 14 denticles per 5 mm in the central and basal sectors of the distal carina respectively (see SOM 2). The denticles are rectangular (larger mesiodistally than apicobasally) and project perpendicularly to the carina. They have slightly convex external margins and become smaller to the base of the crown. The interdenticular space is relatively wide, but there are not interdenticular sulci between the denticles at least in the preserved part of the crown. Subtle transverse and marginal undulations are present in both labial and lingual surfaces. The enamel has a very weak irregular ornamentation (but it is possible that the surface is somewhat worn out).

MG 4813 and 4818 correspond to fragments of the basal part of two relatively large tooth crowns, with estimated CH around 80 mm ( Fig. 20B, C ). Despite fragmentary, these specimens show morphology similar to the previously described tooth, including the shape of the basal cross-section, the size of the preserved fragment of the crown base (see SOM 2), the morphology and number of denticles, as well as the shape and relative extension of the mesial and distal carinae. In MG 4818 the distal carina is straight and placed in the distal surface, but the mesial one seems to project slightly into the lingual surface to the base of the crown. The mesial denticles are quadrangular, with slightly convex distal margins. The denticles are separated by narrow interdenticular spaces and become smaller to the base of the crown. The distal denticles are subquadrangular with slightly convex external margins and are separated by broad interdenticular spaces in MG 4813. On the other hand, the distal denticles of MG 4818 are rectangular and much longer mesiodistally than apicobasally. A clear demarcation between the operculum and the radix is present in all preserved denticles of both mesial and distal carinae. Transverse and marginal undulations are absent in the preserved fragment of the crown in both specimens, but MG 4818 has subtle oblique interdenticular sulci adjacent to some distal denticles on the lingual surface. The enamel has irregular, very subtle texture on both lingual and labial surfaces.

Remarks.—MG 4818 and 4813 are incomplete and distorted, but the size of the preserved fragment suggests that these specimens likely belong to a very large theropod taxon. The size of these specimens (with CH > 75 mm) is only comparable to the crowns of Torvosaurus among the Late Jurassic theropod taxa currently known in the Portuguese fossil record. The number and morphology of the denticles as well as the extension of the carinae are also similar to those described for the lateral and mesial teeth of Torvosaurus ( Hendrickx et al. 2015b, 2020b; Malafaia et al. 2017a). The results of the discriminant analysis classify MG 4818 as belonging to Mapusaurus, MG 4813 to Ceratosaurus , and MNHN/ UL.EPt.8628 to Albertosaurus (see Table 1). The plot obtained in the LDA shows MG 4818 and MNHN/UL.Ept.8628 within or close to the morphospace of Tyrannosaurus , while MG 4813 is in the intersection of the morphospace of different large theropods, including abelisaurids, Torvosaurus , carcharodontosaurids, and Tyrannosaurus ( Fig. 16 ). These results can be explained by the large size of the specimens and the high percentage of missing variables, particularly those related to denticles density. The cladistic analysis of the dentition-based data matrix with constraints and including all studied morphotypes recovered the specimens here grouped in Morphotype 2 in a polytomy within a poorly-resolved Megalosauroidea clade ( Fig. 18A ). The results of the analysis pruning a priori all the morphotypes from the Lusitanian Basin but Morphotype 3 found 3 MPTs (CI = 0.203, RI = 0.463, L = 1318). The consensus tree from these MPTs (CI = 0.198, RI = 0.444, L = 1355) is similar to that obtained in the previous analysis also recovering Morphotype 2 within a large polytomy with several megalosauridae taxa

Fig. 21A ). MNHN/UL.Ept.8628 possibly corresponds to a mesial tooth crown based on its elongation, relatively low labiolingual compression ( CBR = 0.6) and the presence of mesial carina restricted to the apical part of the crown. Only the number of denticles on the central and basal sectors of the distal carina of MNHN/UL.Ept.8628 can be determined, and it is similar to the average number of distal denticles on Torvosaurus , also sharing with this taxon similar denticle shape and the centrally positioned carinae (see Hendrickx et al. 2020b). Furthermore, despite the absence of the crown apex, the preserved part indicates that the specimen would belong to a particularly large theropod taxon ( CH > 75 mm). Except for Torvosaurus , no other taxon currently known in the Upper Jurassic fossil record of the Lusitanian Basin has tooth crowns of this height. Based on this combination of features, Morphotype 2 is here referred to Torvosaurus , which is also consistent with the results of the cladistic analyses. Moreover, based on the paleogeographic and stratigraphic distribution, these specimens most likely belong to the Portuguese species Torvosaurus gurneyi Hendrickx & Mateus, 2014 .

Figures

Fig. 19. Tooth crown (MNHN/UL.EPt.023) attributed to an indeterminate megalosauroid theropod from the upper Kimmeridgian–lowermost Tithonian Praia da Amoreira-Porto Novo Formation, Porto Dinheiro (Lourinhã region, Portugal) in labial (A3), distal (A4), mesial (A5), and lingual (A6) views; detail of the mesial and distal denticles in the apical part of the crown (A1), detail of the enamel ornamentation (A2), detail of the distal denticles in the central sector of the carina (A7).

Fig.2. Geological and stratigraphical context of fossil sites in the Consolação and Bombarral sub-basins, Portugal. A. Geological map of coastal region of Lourinhã and Peniche with localities yielding fossil remains studied in this work (modified from Camarate França et al. 1960; Manuppella et al. 1999a). B. Map of the Lusitanian Basin with the main structural elements and the different sub-basins (sensu Fürsich et al. 2021). C. Simplified stratigraphy of the Upper Jurassic and Lower Cretaceous sequences in the Torres Vedras and Lourinhã costal region and Consolação-S.Martinho do Porto coastal region based on Hill (1988), Manuppella et al. (1999a) and Azerêdo et al. (2010).Abbreviations:Assen., Assenta; Chron., Chronostratigraphy; Fm., Formation; mb., member; l., lower; m., middle; Oxfor., Oxfordian; sb., sub-basin; u., upper.

Fig. 1. Geological map (adapted from Oliveira et al. 1992) showing the Mesozoic levels and the main structures that delimit the different sectors (sensu Ribeiro et al. 1996 and Kullberg et al. 2006) and sub-basins (sensu Fürsich et al. 2021) of the Lusitanian Basin, Portugal.

Fig. 7. Geological and stratigraphical context of the Figeira de Foz and Aveiro region. A. Map of the Lusitanian Basin with the main structural elements and the different sub-basins (sensu Fürsich et al. 2021). B. Geological map of Figueira da Foz and Aveiro region (Aveiro sub-basin) with localities yielding fossil remains studied in this work (modified from Rocha et al. 1981 and Barbosa et al. 2008). C. Simplified stratigraphy of the Upper Cretaceous sequences in the Figueira da Foz and Aveiro sub-basins based on Barbosa et al. (2008).Abbreviations: Chron., Chronostratigraphy; Fm., Formation; mb., member; l., lower; m., middle; sb., sub-basin; u., upper.

Fig. 16. Graphical results of the Linear Discriminant Analysis (LDA) of 581 tooth crowns belonging to twenty-two theropod taxa and the isolated specimens from the Lusitanian Basin studied in this work. Eigenvalue of axis 1 = 8.2989 (which accounts for 67.28% of the total variation) and eigenvalue of axis 2 = 1.129 (which accounts for 9.152% of the total variation). AL, apical length; CBW, crown base width; CH, crown height; DA, distoapical denticle density; DB, distobasal denticle density; DC, distocentral denticle density; MA, mesioapical denticle density; MB, mesiobasal denticle density; MC, mesiocentral denticle density; MCL, mid-crown length; MCW, mid-crown width; MDE, mesiobasal denticles extent.

Fig. 18. Strict consensus trees resulting from a cladistic analysis performed on a dentition-based data matrix and forcing the constrains defined by Hendrickx et al. (2020a) with the five tooth morphotypes from the Lusitanian Basin (A), simplified strict consensus tree resulting from the cladistic analysis pruning a priori all morphotypes from the Lusitanian Basin but Morphotype 1 (B), and simplified strict consensus tree resulting from the analysis pruning a priori all morphotypes from the Lusitanian Basin but MNHN/UL.EPt.023 (C).

Fig. 20. Tooth crowns attributed to the megalosauroid theropod cf. Torvosaurus gurneyi Hendrickx & Mateus, 2014 from different Kimmeridgian to Tithonian localities of Portugal. A. MNHN/UL.EPt.8628, Porto Dinheiro (Lourinhã region). B. MG 4813, Montoito (Lourinhã region). C. MG 4818, Praia de S. Bernardino (Peniche region). Labial (A1, B1, C1), lingual (A2, B2, C2), distal (A5, B4, C4), and mesial views (A6, B3, C3); detail of the distal denticles in the central sector of the carina (A3); basal cross-section (A4, B5, C6, C7); cross-section at mid-height of the crown (C5).

Fig. 21. Simplified strict consensus trees resulting from a cladistic analysis performed on a dentition-based data matrix and forcing the constrains defined by Hendrickx et al. (2020a) pruning a priori all morphotypes from the Lusitanian Basin but Morphotype 2 (A), simplified strict consensus tree resulting from the analysis pruning a priori all morphotypes from the Lusitanian Basin but MG 15 (B), and simplified strict consensus tree resulting from the analysis pruning a priori all morphotypes from the Lusitanian Basin but Morphotype 3 (C).