Tupandactylus imperator ( Campos and Kellner, 1997 )
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publication ID |
https://doi.org/ 10.4202/app.2010.0057 |
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persistent identifier |
https://treatment.plazi.org/id/03A287F7-FF88-115B-FCC9-FB06EF9AFD35 |
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treatment provided by |
Felipe |
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scientific name |
Tupandactylus imperator ( Campos and Kellner, 1997 ) |
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Tupandactylus imperator ( Campos and Kellner, 1997)
Figs. 1 View Fig , 3 View Fig , 4 View Fig .
Holotype: MCT 1622 −R.
Material.—CPCA 3590, an incomplete skull and lower jaw with associated soft tissues.
Emended diagnosis.—Tapejarid pterosaur with an occipital process that reaches about the length of the rest of the skull (measured from the tip of the premaxillae to the squamosals); an extremely large soft−tissue median cranial crest supported anteriorly by a spine−like, caudally inclined suprapremaxillary process; soft−tissue component of the cranial crest composed doi:10.4202/app.2010.0057
of parallel fibers curving in caudal direction; an anteriorly projecting convex blade on the premaxillae and a lower jaw bearing a very deep rounded median mandibular crest with a steep rostral margin forming an angle of approximately 60 ° with the mandible.
Description.—Specimen CPCA 3590 is preserved in four limestone slabs. When the slabs were split the skull was divided along a sagittal plane with considerable bone substance in both slab and counterslab. Here we consider the slabs with bones preserved in internal view as counterslab. The counterslabs contains only a restricted portion of the antorbital part of the cranium (premaxilla, maxilla, anterior process of the jugal, nasal and the proximal extremity of the lower jaw; Fig. 3C, D View Fig ). The two remaining slabs preserve, in addition to the structures mentioned above, both bony and soft−tissue components of the median crest, as well as the dorsal margin of the nasoantorbital fenestra and the distal portion of the lower jaw ( Fig. 3A, B View Fig ). The rostral margin of the premaxilla is exposed in internal view only in the counterslab. The skull is seen in a right lateral aspect and all the bones of the counterslabs are actually remains of the right side of the skull in internal view. The lower jaw is dislocated from its original position, now lying diagonally across the skull covering the middle part of the nasoantorbital fenestra. The rostral tip of the mandible lies adjacent to the anterior bony component of the median cranial crest. The mandible is arranged with its ventral margin placed upwards. Therefore, this structure is preserved in left lateral aspect.
The temporal and occipital portion of the specimen was cut off, probably by quarrymen, and the region posterior to the nasoantorbital fenestra as well as a considerable portion of the soft−tissue cranial crest are therefore missing. The skull has preserved length of 333 mm and is 670 mm high. The lower jaw has a total length of 305 mm. There is only sparse evidence of sutures between bones. The size of the skull, when compared with other specimens referred to T. imperator , is compatible with the hypothesis that the specimen represents a mature individual, although CPCA 3590 is slightly smaller than the holotype of T. imperator (MCT 1622−R; Fig. 1B View Fig ; Campos and Kellner 1997) and the specimen illustrated by Unwin and Martill (2007) is the biggest known so far. It is likely that T. imperator could reach 3–4 m of wingspan, though the absence of postcranial remains associated with this species makes any estimative merely tentative.
Premaxillomaxilla.—The premaxillomaxilla is almost completely preserved but the rostral end of the premaxilla is intact only in the counterslab of the specimen. There is no visible suture between premaxilla and maxilla, which is common among most pterosaurs, even in presumably juvenile specimens, and was previously reported in Tapejaridae ( Kellner 1989; Lü and Yuan 2005). Ontogenetic studies reveal that the fusion between the premaxilla and the maxilla occurs very early in the ontogeny of pterodactyloid pterosaurs ( Kellner and Tomida 2000). The anterior margin of the premaxillary bony crest is badly preserved. In this region the bone is broken, with numerous fragments scattered adjacent to the skull. It is likely that fragmentation occurred before burial. The rostral end of the beak is inclined ventrally at an angle of about 15 ° against the posterior process of the maxilla. The dorsal element of the premaxilla forms the bony component of the median cranial crest as well as a considerable portion of the anterodorsal margin of the nasoantorbital fenestra. In CPCA 3590, and in other skulls referred to T. imperator , the cranial median bony crest rises anteriorly as a plate−like element with an anteriorly projecting convex blade that marks a well−distinguished change in the direction of the anterior margin of the premaxilla, from a sub−vertical to a more dorso−posterior orientation (at an angle of about 15 °). The dorsal−most portion of the premaxillae forms a spine−like dorso−posteriorly oriented process that supports the huge soft−tissue element of the cranial crest. The premaxilla has a very slender posterior process that forms the anterior part of the dorsal margin of the nasoantorbital fenestra. The dorsal margin of the posterior process of the premaxilla is strongly striated. Here, the parallel fibers that compose the soft−tissue median crest originated, with the fibers penetrating the bone, as was observed by Frey et al. (2003) for SMNK PAL 2839.
At the rostral end of the premaxilla there is a dark structure with a smooth appearance when compared with the rough bony surface. This structure is identified as a remnant of a rhamphotheca ( Fig. 4C View Fig ).
Nasals.—In CPCA 3590, the right nasal is preserved in internal view in the counterslab of the specimen and has a triangular outline, with a sharp anterior process. The bone is dorsally articulated with the posterior process of the premaxilla and ventrally forms the dorsoposterior margin of the nasoantorbital fenestra. The frontonasal and the lacrimonasal sutures are not preserved.
Jugal.—Only the slender maxillary process of the jugal is preserved. Together with the posterior process of the maxilla, the maxillary process of the jugal forms the ventral margin of the nasoantorbital fenestra. In CPCA 3590 these bones are partially dislocated in a region close to the mid−line of the total longitudinal extension of the opening. In CPCA 3590 the lacrimal and most of the jugal are broken and the posterior region of the skull, including the frontoparietal and the caudally−orientated parietal process, are missing.
Lower jaw.—The edentulous lower jaw has a total length of 305 mm and does not preserve any sign of sutures. Although the dorsal margin of the dentary part of the mandible is badly preserved, a depression is discernible, following the ventrally turned premaxillomaxilla. The mandibular symphysis extends into a deep ventral bony crest that reaches a maximum height of 93 mm and occupies approximately the anterior half (51%) of the mandible. The margin of the crest is asymmetrically convex with the anterior margin being steeper than the caudal one, almost reaching the rostral symphyseal extremity of the dentary, which has a sharp, very discrete anterior projection. The mandibular rami are longitudinally slender and bear a small retroarticular process. Similar to the upper jaw, the anterior extremity of the mandibles is covered by a smooth unossified structure, likely a remnant of a keratinous rhamphotheca ( Fig. 4D View Fig ). At the middle of the left mandibular ramus there are small filamentous structures of uncertain affinities. Most of the filaments are curved, the biggest ones reaching 8 mm and 0.8 mm thick ( Fig. 4A View Fig ).
Soft−tissue median crest.—The soft−tissue component of the cranial median crest in CPCA 3590 is exceptionally well−preserved and shows a pattern of sub−vertical fibers that begins at the dorsal margin of the premaxilla and extends to the dorsal extremity of the crest ( Fig. 4B View Fig ). At the posterior−most preserved portion of the crest the fibers are vertically arranged for most of their extension, describing a slight caudally directed curvature at the top of the crest. Toward the an−
doi:10.4202/app.2010.0057
terior part of the skull, the fibers become more dorso−posteriorly orientated, the most anterior ones almost reaching the inclination of the supra−premaxillary process. The fibers run parallel to each other with no sign of cross−over. The dorsal margin of the premaxilla is vertically striated, indicating that the fibers mineralize at that spot.
Geographic and stratigraphic range.—The specimen comes from the laminated limestone of the Crato Formation, (Araripe Basin, northeastern Brazil) and was collected by quarrymen at Mina Trinfo (Nova Olinda city, Ceará Province, UTM 24M−0423025E/9212692N). Although the precise stratigraphic horizon from where the specimen was collected remains unknown, the light gray color of the sediment and its style of lithification are compatible with the basal layers of the biomicritic limestone package of the Crato Formation, which is usually interpreted as Aptian ( Pons et al. 1990; Assine 2007).
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