Megalosauripus transjuranicus ichnosp. nov. A new Late Jurassic theropod ichnotaxon from NW Switzerland and implications for tridactyl dinosaur ichnology and ichnotaxomy

A new ichnospecies of a large theropod dinosaur, Megalosauripus transjuranicus, is described from the Reuchenette Formation (Early-Late Kimmeridgian, Late Jurassic) of NW Switzerland. It is based on very well-preserved and morphologically-distinct tracks (impressions) and several trackways, including different preservational types from different tracksites and horizons. All trackways were excavated along federal Highway A16 near Courtedoux (Canton Jura) and systematically documented in the field including orthophotos and laserscans. The best-preserved tracks were recovered and additional tracks were casted. Megalosauripus transjuranicus is characterized by tridactyl tracks with clear claw and digital pad impressions, and notably an exceptionally large and round first phalangeal pad on the fourth digit (PIV1) that is connected to digit IV and forms the round heel area. Due to this combination of features, M. transjuranicus clearly is of theropod (and not ornithopod) origin. M. transjuranicus is compared to other Megalosauripus tracks and similar ichnotaxa and other unassigned tracks from the Early Jurassic to Early Cretaceous. It is clearly different from other ichnogenera assigned to large theropods such as Eubrontes-Grallator from the Late Triassic and Early Jurassic or Megalosauripus-Megalosauropus-Bueckeburgichnus and Therangospodus tracks from the Late Jurassic and Early Cretaceous. A second tridactyl morphotype (called Morphotype II) is different from Megalosauripus transjuranicus in being subsymmetric, longer than wide (sometimes almost as wide as long), with blunt toe impressions and no evidence for discrete phalangeal pad and claw marks. Some Morphotype II tracks are found in trackways that are assigned to M. transjuranicus, to M.? transjuranicus or M. cf. transjuranicus indicating that some Morphotype II tracks are intra-trackway preservational variants of a morphological continuum of Megalosauripus transjuranicus. On the other hand, several up to 40 steps long trackways very consistently present Morphotype II features (notably blunt digits) and do not exhibit any of the features that are typical for Megalosauripus (notably phalangeal pads). Therefore, it is not very likely that these tracks are preservational variants of Megalosauripus transjuranicus or Megalosauripus isp. These trackways are interpreted to have been left by an ornithopod dinosaur. The high frequency of large theropod tracks in tidal-flat deposits of the Jura carbonate platform, associated on single ichnoassemblages with minute to medium-sized tridactyl and tiny to large sauropod tracks has important implications for the dinosaur community and for paleoenvironmental and paleogeographical reconstructions. As with most other known occurrences of Megalosauripus tracks, M. transjuranicus is found in coastal settings, which may reflect the preference of their theropod trackmakers for expanded carbonate flats where food was abundant

The tracks of giant theropods (Jurabrontes curtedulensis ichnogen. & ichnosp. nov.) from the Late Jurassic of NW Switzerland : palaeoecological & palaeogeographical implications

Jurabrontes curtedulensis, a new ichnogenus and species of Late Jurassic giant theropod dinosaur track is described based on very well-preserved and morphologically-distinct tracks, all carefully excavated along federal highway A16 (Canton Jura, NW Switzerland). All trackways were systematically documented including parameter measurements, descriptions, outline drawings, orthophotos and laserscans. Jurabrontes is characterised by sub-equal track length and width, a small anterior triangle, weak mesaxony, three blunt digits (dII-III-IV) with pronounced (sub)triangular claw marks, a rounded heel, and clear phalangeal pad impressions. The combination of features of Jurabrontes is typical for a theropod (and not ornithopod) trackmaker. Jurabrontes is compared to other similar ichnotaxa and unnamed tracks of large theropods from the Early Jurassic to Late Cretaceous, from which it is clearly different. The sheer size of the largest tracks, that are amongst the largest worldwide and of similar size to Tyrannosauripus from the Late Cretaceous, suggests a 'megalosaurid' or large allosaurid theropod as a trackmaker. The presence of such large theropod tracks in tidal-flat deposits of the Jura carbonate platform and associated with small to large sauropod tracks has important palaeoecological implications for the dinosaur community and for palaeoenvironmental and palaeogeographical reconstructions. Jurabrontes - urn:lsid:zoobank.org:act:B482D2AF-637A-4B2D-8B0B-FEAD54CA2A26 J. curtedulensis- urn:lsid:zoobank.org:act:30D45944-5A2B-45E1-89B9-20298E475D51

<i>Megalosauripus transjuranicus</i> ichnosp. nov. A new Late Jurassic theropod ichnotaxon from NW Switzerland and implications for tridactyl dinosaur ichnology and ichnotaxomy

<div><p>A new ichnospecies of a large theropod dinosaur, <i>Megalosauripus transjuranicus</i>, is described from the Reuchenette Formation (Early–Late Kimmeridgian, Late Jurassic) of NW Switzerland. It is based on very well-preserved and morphologically-distinct tracks (impressions) and several trackways, including different preservational types from different tracksites and horizons. All trackways were excavated along federal Highway A16 near Courtedoux (Canton Jura) and systematically documented in the field including orthophotos and laserscans. The best-preserved tracks were recovered and additional tracks were casted. <i>Megalosauripus transjuranicus</i> is characterized by tridactyl tracks with clear claw and digital pad impressions, and notably an exceptionally large and round first phalangeal pad on the fourth digit (PIV1) that is connected to digit IV and forms the round heel area. Due to this combination of features, <i>M</i>. <i>transjuranicus</i> clearly is of theropod (and not ornithopod) origin. <i>M</i>. <i>transjuranicus</i> is compared to other <i>Megalosauripus</i> tracks and similar ichnotaxa and other unassigned tracks from the Early Jurassic to Early Cretaceous. It is clearly different from other ichnogenera assigned to large theropods such as <i>Eubrontes</i>–<i>Grallator</i> from the Late Triassic and Early Jurassic or <i>Megalosauripus</i>–<i>Megalosauropus</i>–<i>Bueckeburgichnus</i> and <i>Therangospodus</i> tracks from the Late Jurassic and Early Cretaceous. A second tridactyl morphotype (called Morphotype II) is different from <i>Megalosauripus transjuranicus</i> in being subsymmetric, longer than wide (sometimes almost as wide as long), with blunt toe impressions and no evidence for discrete phalangeal pad and claw marks. Some Morphotype II tracks are found in trackways that are assigned to <i>M</i>. <i>transjuranicus</i>, to <i>M</i>.? <i>transjuranicus</i> or <i>M</i>. cf. <i>transjuranicus</i> indicating that some Morphotype II tracks are intra-trackway preservational variants of a morphological continuum of <i>Megalosauripus transjuranicus</i>. On the other hand, several up to 40 steps long trackways very consistently present Morphotype II features (notably blunt digits) and do not exhibit any of the features that are typical for <i>Megalosauripus</i> (notably phalangeal pads). Therefore, it is not very likely that these tracks are preservational variants of <i>Megalosauripus transjuranicus</i> or <i>Megalosauripus</i> isp. These trackways are interpreted to have been left by an ornithopod dinosaur. The high frequency of large theropod tracks in tidal-flat deposits of the Jura carbonate platform, associated on single ichnoassemblages with minute to medium-sized tridactyl and tiny to large sauropod tracks has important implications for the dinosaur community and for paleoenvironmental and paleogeographical reconstructions. As with most other known occurrences of <i>Megalosauripus</i> tracks, <i>M</i>. <i>transjuranicus</i> is found in coastal settings, which may reflect the preference of their theropod trackmakers for expanded carbonate flats where food was abundant.</p></div

Methodology of track and trackway labeling and parameter measurements.

<p>Note that the pictured tridactyl track does not correspond to <i>Megalosauripus transjuranicus</i>, it is a schematic track with a typical theropod phalangeal pad configuration of 2-3-4 for dII-III-IV, respectively. <b>(A)</b> Track length (PL) and width (PW), labeling of digits (d), phalangeal pads (P) and claws (C). The internal track outline corresponds to the (interpretation of the) actual impression of the foot. <b>(B)</b> Interdigital angles (da) and anterior triangle (AT). PW is the width and te the length (measured perpendicular to the width) of the anterior triangle, which in the present case has an obtuse angle for the anterior apex indicating a low mesaxony. <b>(C)</b> Digit lengths (L) and widths (W). <b>(D)</b> Trackway parameters. Labeling of trackways always starts with L1; if L1 is missing R1 is the first number used. α is the rotation (in this case outward and thus a positive value) of the track (long axis) with respect to the next stride line. LP and RP are left and right pace, respectively; S is stride; WAP is width of the angulation pattern (measured perpendicular to the stride length; [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0180289#pone.0180289.ref020" target="_blank">20</a>]), γ is pace angulation. The progression is a calculated value (with the Pythagoras’s theorem) and it indicates the forward movement of the trackmaker in the direction of the trackway during one footfall (pace) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0180289#pone.0180289.ref020" target="_blank">20</a>]. Progression is only half of the stride in the case of completely regular trackways. The reference point for the trackway parameter measurements is on the tip of the third digit (without the claw where preserved).</p