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Home , Marmoretta, Megachirella, Megalancosaurus

Rivista Italiana di Paleontologia e Stratigrafìa November 2003

A NE\T LE,PIDOSAUROMORPH FROM THE MIDDLE OF THE DOLOMITES (NORTHERN ITALY)

SILVIO RENESTO' & RENATO POSENATO'

Receit,ed July 27,20A2: accepted January 24,2AA3

Key uords: Reptilia, Dìapsida, Lepidosaurómorpha, new , but our understanding of the early evolution of the Lepi- description, Anisian, Mìddle Triassìc, Dolomites, Northern Italy dosauria is vague, particularly for the , that have a record dating only to the (Evans 1984, Abstact. A new genus and species of reptile is described. The specimen n-as collected from the Anisian () succession 1988, l99l; Valdman & Evans 1994). Most authors (e. of Monte Prà della Vacca (Kùhwiesenkopf) ìn the Dolorrites of Braies g. Evans 1984, 1988; Gauthier et ai. i988), regard Per- (Bolzano/Bozen, Northern Itall'). Despite being incomplete, the specimen mian and Triassic taxa like Paligwana and kueheneosau- shows enough characters to allor. ìts placement *'ithin Lepidosauriformes, rids, previously considered as primitive members of the close to the gents Marmoretra. The importence of this find Squam.rra g. l975, 1977), neirher as primitive lies in the great rarity' of lepìdosaurifonns of Anisian age, rn epoch ap- 1e. Crrroll proximating the appearance of the first members of the true Lepidosaurìa nor lepidosaurians, representing instead independ- (rhyncocephalians and squamates). The new genus may thus add kno*'l- ent radiations of squamate-like on the stem of edge to the diversity of early lepidosaurians. Some characters of the skele- the . ton, mainly forelimb, a terrestrial, perhaps arboreal life of the suggest style. Evans (1991) and Valdman t{ Evans (1994), con-

Riassunto. Viene descritto un nuovo genere di rettile diapside rin- sidered from the Middle Jurassic of England venuto nella successione anisica (Triassico Medio) di Monte Prà della Vec- as a probable sister taxon of and suggested ca (Kùhwiesenkopf) nelle Dolomiti, presso Braies (Bolzano). Lesemplare, that it must represent a late survivor of a lineage dating benché incompleto, consetra caratteri sufficienti per una classificaz-ione, back to the Early tiassic. consentendo di ascriverlo ad un nuovo genere e specìe dì Lepìdosaurifor- recent years an Anisian (Middle Triassic) ho- mes, probabilmente rffìne al genere Marmoretta del Giurassico Inferìore In inglese. La particolare importanza di questo ritrovamento sta nella estre- rizon, rich in fossil plants and vertebrates has been dis- ma rarità di lepidosauriformi del Triassico Medio, momento coincidente, covered by Mr. Michael \íachtler in the Braies (Prags) od immediatamente successivo, alla comparsa dei Lepidosauria evoluti dei Dolomites (Northern Italy). For this reason a research qtah sn Marmoretta che l'esenplare descritto possóno r:rppresentare un project, supported by the Museo Archeologico e Natura buon modello per la forma ancestrale. Alcuni adattamenti dell'arto ante- riore fanno pensare ad un adattamento alla vita arboricola. of Bolzano (Alto Adige) under the leadership of Prof. C. Broglio Loriga from the Ferrara University has been start- ed, with the aim to study the taxa collected in the deposit lntroduction and the palaecology and paleoenvironmental evolution of the succession. In this fossiliferous horizon, Mr. Michael According to most re cent definitions (Evans 1984, Wachtler also recovered a partial skeleton of a diapsid rep- 1988; Gauthìer 1984; Gruthier er al. 1988) the Lepido- tile. Its description and taxonomic assessment is the aim are considered as the group comprising Rhyn- of the present paper. chocephalia (Spbenodon and its fossil relatives) and Squa- mata, (Iizards, and amphisbenians) along with their immediate common ancestor. The fossil history of Rhyn- Stratigraphical setting and age chocephalia can be followed back until early (Fraser & Benton 1989), suggesting thrt the primary di- The reptile was collected from a rich plant horizon, chotomy between rhynchocephalians and squamates oc- that outcrops on the western slope of Monte Prà della curred earlier, possibly in the Early Triassic (Evans 1 991 ) Vacca (Kùhwiesenkopf in German) in the Braies/Prags

Dipartimento di Biologia Strutturale e Funzionale, Università degli Stud:i dell'Insubria, Va Dunant 3, Varese, Italy E-rnail silvìo.renesto(r.guninsubria.it Dìpartimento di Scjenze della Terra, Università di Ferrara, C.so Ercole I d'Este 32, 441.00 Italy. E-mail [email protected]ìfe.ìt S. Renesto k R. Posenato

Fig. 1 - Monte Prà della Vacca/ Kùh- Monte Prà della Vacca / Kuhwiesenkopf section wiesenkopf section :rnd strati- graphical setting of Megachirel- Ia 'oacbtleri sp. n. (black draw- Brunìco ing). General column ad:rpred

Bolzono and rnodìfied frorn Bechstàdt & Brandner (1970; enclosure ) ) \.'l 2). From Broglio Loriga et al. irrenro ,j1\ ^ ,, 2002 b, nodified. \P ---\Ss"i"%;

Z H ,& a Plant H horizon z %

0 Trunk bed 'a a L-l 't L L t z 0

Brachiopod bed :

Leoeno a ']::..,L-\-rJ WCW OnO nOOUlOr .l E--tai Conglomerote lq*iì" limesione ond mor (J l Sondsione, sillsfone ff Tl, Bedded ond L.=r- - 'J ond corbonote siltstone L|ri mossive limesîone I r aì F l Sillv mofl ond W Ptont beoring bed eil+\ /-m^r \/ | Lmact^^ò ono ponÌ remotn -

Dolomites (northern Dolomites) (Fig. 1). This area has The deposit is located in the lower part of the Ani- been famous in the paleontological literature since the sian basinal succession, which has variously named: Pragser 19'1'century, mainly for the Anisian (Pelsonian) brachio- Schichten (Pia 1937) , siltitische Mergel und Knollenkalke pods and ammonoids of the "alpiner Muschelkalk" (Lo- (: Prrgser Schichten p.p.) (Bechstàdt & Brandn er 1970), retz 1875; Mojsisovics 1829, 1882; Bittner 1890). In ad- Dont Formation of the Braies Group (Pisa et al. 1928; Fois dition, the Braies/Prags Dolomites have made fundamen- & Gaetani 198,t; De Zanche et aL. 1993; Senowbari-Daryan tal contributions concerning the Dolornites stratigraphy et al. 1993; Delfrati et al. 2000). Senowbari-Daryan et al. (e.g. Pia 1937; Bechstiidt & Brandner 1970; De Zanche (1993) considered the Dont Formation in the Braies area et aI. 1992; Senowbari-Daryan er al. 1993). as an hemipelagic carbonate-terrigenous sequence of mar- Neru lepidctsawromoryh from the Triassic of Dolomites 165 ginal basin environment, about a hundred metres deep. In Systematic paleontology (Silvio Renesto) the Monte Prà del1a Yacca / Kùhwiesenkopf section, the Reptilia Dont Formation is more than 200 m thick, and the fossili- Diapsida ferous horizon is placed at about 75 m from its base (Bro- Lepidosauromorpha glio Loriga et al.20A2 b), which is represented by a massive carbonate platform (bed K3, enclosure 2 of Bechstàdt & Lepidosauriformes Brandner 1970; Fig. 1) belonging to the Algenwellenkalk gen. n. unit of Bechstàdt & Brandner (197q, now attributed to the Gracilis Formation (De Zanche et aI. 1992; Senowbari- Type species: Megachirella "oachtleri sp. n. Daryan et a1.1993) (Fig. t). The plant horizon, placed just above bed K 11 of Derivatio Nominis: Mega (large) cheiros (hand): little u ith l.rrge h:nd: referred shape Bechstàdt & Brandner (1920, enclosure 2), is about one to the and robustness of the manus. Diagnosis: As for type as only known species. meter thick; plants are concentrated in siltstone, marly siltstone and carbonatic siltstone layers some cenrime- tres-thick (Fig. t). The fossiliferous layers have a lens Megachirella wachtleri sp. n. shape, therefore their number and thickness may change laterally. They are alternated with silty and marly lime- Derivatio nominis: declicatcd to Mìchael \Wachtler rvho dis- stone layers, containing sparse terrestrial plant remains. covered the specimen. Marine organisms (fishes, bivalves, brachiopods) ammo- Holotype: Specin-ren KUH 1501 of the catalogue of the Museo Archeologia e noids and gastropods) are present, but not abundant, N:Ltura dell'Alto Ac1ìge, Bolzano (Bozen) Italy. Age: Anisian (Middle îiassic). throughout the horizon. Occurrence and preservarion Horizon and locality: Plant-rich level, above bed K I 1 of Bech- of terrestrial and marine rogerher musr be related stàdt & Brandn er (197A, enclosure 2) Dont Formation, Monte Prà del- to very rapid burial events caused by gravity flows with- la Vacca / Kùhwiesenkopf area, Braies (Prags), Bolzano(Bozen), Alto in a marine basin, connected with hear,y storms in the Adige, Northern Italy. terrestrial domain (Tintori et al. 2001; Broglio Loriga et Diagnosis: Small diapsid reptile with a rather large al.2002 a, b). , moderately elongate neck and stout anterior limbs. At the base of the deposit, a layer of carbonatic silt- Upper temporal fenestrae large, lower remporal bar in- stone, about 3O cm thick, represents a marker bed, easily complete, frontals fused forming a wide flat table, pa- recognizable because its upper surface is rich in trunks, rietals narrow and possibly fused, parietal foramen ab- roughlv N-S oriented (Fig. 1). Large rare re- but plant sent; postfrontal sma1l, postorbital with elongate posre- mains (trunks) are also presenr ar the top of a limestone rior process, squamosal triangular and stout with ventral bank situated about two metres below (Fig. 1). This unit cotyle for a movable quadrate; jugal with short, caudally of nodular, massive wackestone and packstone contains pointed posterior process, quadratojugal absent, qurd- a rich marine assemblage with foraminifers, byssate bi- rate lateromedially wide with mobile articulation with v alv e s (My s i di op tera) and brachiop o ds (P un cto sp irtferella the squamosal, stout ascending process and prominent and Angustothyrisl. pterygoid flange anteriorly, presence of a deep otic notch. The deposit is characterizedby a rich assemblage Lower jaw stout bearing robust subpleurodont teeth. Cer- of plants representing by at least 17 genera (Kustatscher vical vertebrae longer than dorsal ones. Vertebrae amph- et al.2002; Broglio Loriga et aI.2Aa2 b). in addition, rare icoelous, with square neural spines and stout transverse specimens of marine and freshwater fishes (Tintori et processes. Presence of a notch between prezygapophys- al. 2001), ammonoids (Sturia sp.), bivalves ("Prospond- es. Dorsal ribs single headed, humerus stout and distally ylui' comptus Goldfuss), and gastropods have been dis- expanded covered. bearing complete ectepicondylar and entepi- condylar foramina, presence of ulnar patella, presence The Dont Formation of the Dolomites is tradition- of lons and stout unguals forming sharp c1aws. ally considered Pelsonian Illyrian in age (Delfrati et al. 2OOO, with ref.). The secrion of Monte Prà de1la Yacca / Kùhwiesenkopf has been dated mosrly on rhe basis of brachiopod assemblages by Bechstàdt Er Brandner (1970, tab. A). The deposit is situated just above the brachio- pod horizon 2 and below the brachiopod horizon 3 (Fig. 1), both referred to Pelsonian (Bechstàdt & Brandner 1920) . The same age is also supported by the benthic fo- Plate I - Megachirella -sachtleri gcn. et sp. n.; KUH 1501 holotype. raminifera (Broelio Loriga et al.2Aa2 b) . Therefore, the Scale bar equals 1 cm. stratigraphic se€iment bearing the deposit belongs ro the Plate 2 - À,'legacbirella zuachtleri sen. er sp. n.; KUH 1501 holotype. Pelsonian (Anisian, Middle Triassic) (Broglio Loriga et A) right anterior limb; B) skull; C) detajl of Jett qurdr.rte, al.2002 b). D) right carpus. Scale bar equals 0.5 cm. S. Renestr.t k R. Posertato

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I'1.2 468 S. Rettesto t< R. Posenato

Tab. 1 - Measurements taken on the specimen frontals form a rather wide and flat table ornamented by

Lensth of the axis 6 mnr small tubercles, the left portion of the table is incomplete. Lensth of the fourth cervical vertebra'l .l mn.r However, the preserved portion is wide enough to detect T enr.th ol-rhe forrrih dorsal rcrr. bra' 3.2 mn.r that no suture between frontals is present. The posterior Lenqth of the rieht humerus 12.8 mnr margins of the frontals form a zrgzag suture with the p.r- Maximum width at the distal head of the rjght hurnerus 6mm rietals. The parietals are narrow but deep, anteroposteri- Leneht of the risht ulna 10 mm orly elongate and approximately two times longer than '' rhe lengrh of rhe verrcbrae quoted here is referred to the distance wide; a faint line runs between the two bones, but it is betlveen the ;rnterior and posterior cnds of the neurrl rrchcs (zy- more probably a fracture and it is feasible that the two gapophyses excluded) since the centra are obscured bv matrix or other bones. bones where they are fused together. The parietals border medially an upper temporal fenestra which is longer than wide. The general outline is superficially similar to that Description of Marmoretra (Evans 1991;\laldman & Evans 1994), but is ab- The specimen (P1. 1, 2) is exposed in dorsal view, the peculiar high parietal crest of this latter genus apart for the right anterior limb which is exposed on ven- sent in our specimen. No pineal foramen can be detected tral view. The skeleton is incomplete but articulated. The between the parietals; if present it could have been placed entire snout region is missing, along with the posterior ciose to the frontoparietal suture. The postorbital is "Y" half of the body, the pelvic girdle and the posterior limbs. shaped with a narroq very elongate squamosal process. The right anterior limb is complete, but its distal portion The postfrontal enters the upper temporal fenestra, but it was originally overlapped by ribs. The left humerus is the cannot be described in detail since it is largely covered by only preserved element of the left anterior limb. Unfor- the displaced frontal plate. The jugal is a narrow sub-tri- tunately a Iayer of pyrite crystal encrusts many bones, angular bone, with a curved orbital border. The posterior especially in the carpal region and at the articulation be- margin of this bone is deeply concave and bears l point- tween vertebrae and ribs. The pyrite has been carefully ed, free-ending quadratojugal process, indicating that the removed only in those areas where the detachment of the lou'er temporal fenestra was ventrally open. The quadra- crust did not damage the underlying bone. tojugal is absent. The left squamosal is almost completely crushed and partially encrusted by pyrite crystals, the right The skull one is detectable (even if disarticulated). It is stout and As noted above, the snout region and the anterior widens in its lateral portion where it houses ventrally the half of the orbital region are missing. Only the posterior concavity which forms the articular area for the quadrate; region of the frontals is preserved (P1.28; Fig.2). The a narrow quadrate descending process points anteriorly to

Fig.2 - Mega.hirella -'a,hrÌcri e.cn. er sp. n.; KUH 1501 holotype. A) dr:rn-ing of the preser-ved por- tions of the skull; scale bar cqLrrl. lcm. B7 tcnt:tite re- construction of the preserved portion of the skull in later- al (left) view. Abbrevìations .tre: .r; .rngul.rr: lr, .rrticulan ch; cer':iohlrlr dJ denr:rvr Ir frontal; j) jugal; mx) maxilla; B po pa) parietal; pf) postfrontal; nf po) postorbital; pop) process of rhc opi.rhotic: prrt prerrt- sq icular; q) quadrate; sq) squa- mosal. Ne",,u lepidosawromolph from the Triassic of Dolomites 469 meet the postorbital and a more robust one extends me- tween exoocipital and paroccipital cannot be detected. dially to reach the parietal, forming the posterior border On the left half of the skull some smooth bones are of upper temporal fenestra. In its general shape (Pl. 2 C; visible, they are probably the palatine and the pterygoid Fig. 2) it recalls the elements figured by Robinson (1962) exposed on their dorsal side, their preservation, however, and Colbert (97a) for Kuehneosaurus and, at a lesser ex- is too poor to allow any description. tent, Icarosaurus. The quadrates (Pl. 2 C; Fig. 2) are deformed being Lower iaw somewhat flattened dorsoventrally due to compression, Only few fragments of both dentaries are detecta- but their morphology is clearly visible: they show a con- ble, however it can be noticed that they were rather deep, vex, rounded dorsal articulation for the squamosal and a giving a robust appearance to the lower l'aw. Few, stout large double ventral condyle for the articulation with the teeth are preserved, placed on a shelf in the lingual side lower jaw. Posteriorly the bone is deeply embayed, form- of the dentaries, suggesting a subpleurodont implanta- ing part of the middle ear cavity. Its anterior margin is tion. The surangular and the angular are very elongate, prominent eiving to the bone a general outline that re- prearticular is long and stout, the articular bears a wide calls that of kuehneosaurids, particularly Kuehneosaurus condyle for the quadrate and continues posteriorly with (Robinson 1962; Colbert 197a) and some lepidosaurs. It a prominent retrolnicular process. can be suggested that the quadrate was mobile, but it is not possible to ascertain which was its degree of mobil- Vertebrae and ribs ity vrith respect to the pterygoids and, as a consequence, The first twelve vertebrae are preserved articu- it cannot be stated if there was a true streptostylic pat- lated in the specimen, followed by a gap in the stone tern or the mobility of the bone was limited as in kueh- slab, which is followed by three other vertebrae, these neosaurids (Evans 1984). latter belonging to the mid region of the trunk. The The occipitai region is partially exposed, the opis- cervical series consists of six vertebrae which are long- totic bears strong paroccipital processes; the sutures be- er than the dorsal ones (Tab.1). The atlas can hardly be

Fig. 3 - Megachirella u,achtleri gen. et . sp. n.; KUH 1501 holotype. Anrerior dor'al rcgion rs pre- served. The black area repre- sents a crack in the slab; rhe gre)r one the area covered by p1 rite I.rlcr. \bbrer irtion' lre: cl) clavicle; d1) first dorsal ver- tebra, d2) second dorsal ver- rebr.r: icl; po'terior rip of rhe stem of the interclar.icle; sc) tip of the dorsal blade of the scapula; st) sternal plate. Scale bar equals 1 cm. 474 S. Renesto tt R. Posenato

seen because it is covered by skull bones and partial- ly overlapped b1'the following axis. This latter is very elongate and stout, as rn Marmorettd (Eyans 1994). The neck is a little telescoped so that the posterior end of each centrum overlaps for a little extent the anteri- or end of the following vertebra, obscuring details of the zygapophyses, but permitting to detect part of the posterior articular surface of the centrum. This latter is slightly concave. The neural arch is wide and bears a low neural spine. Zygapophyses, where visible, seem to bear horizontally directed articular surfaces, thus al- lowing a good lateral mobility to the neck, while reduc- ing probably vertical movements. The dorsal vertebrae (Fig. :) bear low neural spines and well developed neu- ral arches, the zygapophyses are flat and with horizon- tally directed articular facets. There are'no traces of a zygosphene-zygantrum system, but this may be due to poor preservation. In some dorsal vertebrae a short but stout transverse process spring out laterally in the mid- enf dle of the vertebral body. The cervical ribs are slender and rather elongate, they run parallel to the axis of the vertebral column until the fourth/fifth cer-vical vertebra. IJnfortunately the rib head is always covered by n-ratrix or overlapping vertebrae. Fìg. 4 - Megachirella zuachtleri gen. et sp. n.; KUH 1501 holotype. The anterior dorsal ribs are long and robust, deep- Right humerus in dors:rl vicw. Abbreviations :re: dpc) del- ly arched and hollow, as shown by the by the collapse topectoral crest, ecf) ectepicondylar foramen, enf) entepi- condr l:r for.rrren: upl Lrln.rr p.riell:. Sc.rl. b:r eqrrals 0.5 crn. of the proximai portion and by the filling of the origì- nal cavity by white crystals of calcium carbonate in the distal part of some ribs. Careful removal of the Jayer of pyrite crystals that encrusted the proximal portion of Anterior limb most vertebrae and of the centra revealed that the dorsal The right humerus is exposed in ventral view (Fig. ribs are holocephalous. \When removing the distal por- a) . The shaft of the bone is twisted so that the proxin-ral tion of some ribs to clear the carpus, the ribs revealed to head lies at a 90'angle with respect to the distal one. The be hollow, thin walled, with the cavity filled with calcite proximal head is well developed and anteroposteriorly crystals. Several thin gastralia are exposed on the right compressed. The distal head is very expanded (Tab. t) side of the specimen where the overlying ribs have not and flattened dorsoventrally. The ectepicondyle bears a been preserved. foramen, while the entepicondyle is perforated by another elongated foramen which opens in a depression on the Shoulder girdle ventral surface of the bone. The shaft is cylindrical and The shoulder girdle is almost completely obscured narrow. A distinct rounded and convex bony structure by vertebrae and ribs thus very little can be seen. The lies close to the anterior end of the distal articular mar- right clavicle almost entirely exposed in its enterior gin of both humeri. It cannot be thc capitellum (sensu view: it is a rather stout, crescent shaped bone taper- Romer 1956) since it lies close to the articular area for ing at each end. Two stout vertically oriented struc- the ulna and apparently it does not even belong to the tures represent the dorsal portion of the scapular blades, humerus, being instead separate. It is tentatively identi- their robustness suggest that these bone were well de- fied here as an ulnar patella (ser-rsu Haines 1969), that is veloped; the exposed portion shows a gently concave a sesamoid ossification which is frequently found in lep- anterior outline. Posterior and ventr:rl to the last the idosaurs. The ulna has a narrow shaft that is nearly cir- dorsal ribs, two paired plate-like structures are partially cular in cross section. Its proximal head is expanded and visible, separated from each other by a rod-like struc- anteroposteriorly flattened, ending with a convex porous ture which ends with a rounded tip. On a topological surface. Thc proximal heads of the ulna and radius were basis the paired structures may be interpreted either covered by ribs but were exposed when some ribs were as the posterior portion of paired sternal plates or less removed in order to access the carpus. The radius is a probably, of wide coracoids. The narrow and pointed narrow featureless bone with a straight shaft; its distal structure represents the posterior tip of the stem of head is more expanded than the proximal one. The ulna the interclavicle. is longer than the radius and also more robust. The dis- Neu lepidosauromorph from the Triassic of Dolomites +71 tal surfaces of both radius and ulna are encrusted by the ?fifth distal carpal is apparently very small. The first and layer of pyrite crystal that could nor be removed. It can- fifth metacarpals are much shorter and stouter than the not therefore be ascertained whether distinct epiphyses others. The distal head of the first metacarpal bears a were present or not. The distal margin of the ulna shows weli developed trochlea allowing greater mobility of the a slight embayement of its medial margin, where it con- proximal phalanges, and suggesting a srrong grip. Meta- tacts the intermedium. carpals I-IV are only partially visible, but they appear as The carpus and part of the manus (Fig. 5) are vis- eiongate rod-like bones. The fifth metacarpal articulates ible. The carpus is made up by several elements and its with the fourth distal carpal along the medial marsin of pattern is not easily interpreted, owing to the presence its proximal end. The manus has been preserved with dig- of the layer of pyrite crystals which make it rather diffi- its contracted, i. e. the phalanges do not lie flat but, are cuit to see the boundaries between elemenrs. In addition, verticalÌy oriented in the matrix, excepr for rhe unguals some displacement has occurred among carpal bones and which are horizontally placed above the basis of the dig- thus the identification of some elements must be consid- its as if they were grasping something. For this reason no ered tentative. Distal to the radius a laterally expanded phalanges are visible apart the unguals, with the cxcep- bone is interpreted as the radiale. Proximal to this latter tion of the first digit which was cleaned laterally: it con- an elongate intermedium conracts the ulna and distally sists of two phalanges, the last one being a long, pointed the medial centrale, a tiny rounded bone almost identi- and stout claw. The unguals of the following three digits cal in shape and size to the lateral centrale. Lateral to are also very stout, elongated and sharply pointed, sug- the intermedium there is a large rounded bone, here in- gesting that the manus was proportionally very wide and terpreted as the ulnare. However, since this area is cov- with good grasping abilities. ered by the pyrite layer, it is not possible to determine whether this layer conceals a small pisiform. The medi- Taxonomic assessment al centrale does not reach the fourth distal carpal as in younginoids (Carroll 1988). At least four distal carpals As can be inferred from the description above, all are present, the fourth being by far the largest one. The preser-ved characters of Megachirella gen. n. fit the diagno-

Fìg. 5 - Megachirella udchtleri gen. et sp. n.; KUH 1501 holotvpe. Right carpus ìn ventral (pal- mar) view. In grey thc area corereJ br pvrite cr\ \îiìì\. Abbreviat:ions are: i) interme- ciiurn, lc) lateral centrale; mc) rredial ccntralc; ?pis) pisiform; r) radius; ra) radiale; u) ulna, ul) ulnare; 1-5 distal carpals; I- V rletacarpals. Scalc bar equ:rls to 0.5 cm. ?pis-mc

lc

?s

V

m 172 S. Renesto k. R. Posenato

sis for advanced diapsids as defined for instance by Ben- logenetically informative or, more probably, as a primi- ton (1985) and Evans (1988). According to most authors tive condition, as for the moderately elongate neck, as it (e. g. Gauthier i984; Benton 1985; Evans 1988; Carroll is found in Marmoretta (Evans 1991). Other characters 1988) most diapsids fall rvithin one of two major clades, speak against close relationships with rhynchocephalians. (prolacertiforms, rhynchosaurs, ahd Namely: the few preserved teeth are stout but not achro- ) and Lepidosauromorpha which comprises sq- dont and there are no remains of a palatine tooth row. At uamates, rhynchocephalians and other more basal taxa like present knowledge, Megacbirella gen. n. can be considered youn ginids, S awro stern on Kuehneos auridae, Paliguan a and with some confidence as belonging to Lepidosauriformes, Marmoretta (Evans 1988, 1991, 1994). but any attempt to clarify better its taxonomic position is \fith reference to the characters sets proposed by tentative due to the incompleteness of the skull and poor Evans (1984, 1988, 1991) and Gauthier et al. (l9SS) for preservation of postcranial elements. Some resemblanc- diapsid phylogeny, Megacbirella gen. n. does not show es with Marmoretta Evans (1991) are present, namely: any significant synapomorphy of the Archosauromorpha, large upper temporal fenestrae, lower temporal bar incom- while it shares some of the derived characters diagnosing plete, frontals and possibly also parietals fused, separated the Lepidosauromorpha, namely: a postfrontal which en- postfrontals and postorbitals, weakly pleurodont teeth. ters the upper temporal fenestra with loss of postorbital- Unfortunately, the incompleteness of the skull in Meg- parietal contact, the presence of paired sternal plates, and achirella gen. n. and the scarcity of postcranial elements an interclavicle with an elongate posterior stem. in Marmoretta do not allow a further clarification of the Within Lepidosauromorpha, Megacbirella gen. n. relationships between these two taxa. may be nested within a more restricted assemblage, the Lepidosauriformes (sensu Gauthier et al. 1988) which compris e s (Pal i guana, Ku eheneos auridae * M arm o r etta * Mode of life Lepidos.ruri.r. Evans 199 l1 on the brsis oI the pre'ence of the following derived characters: prominent conch Evans (1991) and Waldman & Evans (1994) sug- formed largely from quadrate, quadrate bowed in lateral gested an aquatic life style for Marmoretta,l:ased on the vieq long paroccipital process which reaches the quad- abundance of bones in a predominantly aquatic assem- rate. large retrorrticular proce\s. qu,rdrrte condyle ex- blage quoting also the peculiar structure of the temporal tending below occipital condyle, ectepicondylar foramen regions of the skul1, with large fenestrae and an high pari- complete, first and fifth metacarpals shorter than second etal crest as consistent with this intepretation. Megachirel- and fourth. la gen. n. does not show any skeletal correlate which can Megachirella gen. n. shows some superficial resem- be considered unequivocally as an adaptation to aquatic blance to members of the Kuehneosauridae, like the loss 1ife. Many characters speak instead for terrestrial habits, of quadratojugal, an incomplete lower temporal bar and like the robustness of the fore-limbs, the height of the the possible presence of a mobile quadrate. However, scapular blade, the high level of ossification of the car- other key characters that could nest Megacbirella gen. n. pus and the size and shape of the claws. In addition, the rvithin Kuehneosauridae are either unknown (confluent presence of hollow ribs also speaks against aquatic hab- nares) or absent, like the shortening of cervical vertebrae, its since aquatic usually show pachyostotic, or at the elongation of the transverse processes of the dorsal least robust, ribs and massive gastralia which act as a bal- r'"rt"h."" rh" h"i.ht oI the neural arches and the ores- last, helping sinking into water. It is thus our opinion that ence of platycoelous vertebrae. Megachirella gen. n., with the collected specimen represents an allochthonous ter- its moderately elongate neck and stubby but short trans- restrial element transported, together with plants, within verse processes seems to be more similar to M(umoretta a marine marginal basin environment. During the Pelso- (the sister group of the Lepidosauria according to Evans nian, emerged lands with fluvial areas and low relief are 1991, 1994). The pattern of the carpus oÍ Megachirella recorded few kilometres south- and westward from the gen. n., if the proposed identification is correct, reveals Kùhwiesenkopf / Monte Prà della Vacca area (Bosellini some similarity with that of Sphenodon.In fact it shows 1968; Senowbari-Daryan et al. 1993). a proximodistally compressed radiale and the exclusion Further inference about life style of Megachirella of the medial centrale from the inner margin of the car- gen. n. may be obtained by analysis of the pattern of the pus (Romer 1956; Carroil 1988). Rhynchocephalians are manus: the phalanges are stout and with well developed known from the Middle Triassic (Fraser & Benton 1989) articular surfaces at least for the unguals; these latter, but the pattern of their carpus is mostly unknown since when covered by horny sheats, surely formed very long most Triassic genera are found as isolated bones, thus the curved and sharp claws, more useful in a terrestrial envi- tiny, grain-sized carpal bones mav escape sieving or are ronment rather than in an aquatic one. The wide base of difficult to identify and interpret (Evans, pers. comm.). the claws house d the insertion of powerful flexor mus- The similarities betn'een the carpus of Megacbirella gen. n. cles, a pattern which allows both a strong grip and using and that ol Sphenodon may either be considered as phy- the claws as clinging devices, especially if these latter are Neru lepîdosauromotph from the Triassic of Dolomites 473

Iaterally compressed (Hildebrand 1974;Cartmill tlSS) as Acknotuledgemeruls. Ourwlrmest thanks to Susan E. Evans (Lon- occurs tn Megachirella gen. n.. However, the rest of the don) and Nicholas C. Fraser, (Martinsville) r.ho reviewed an earlier skeleton ol Megachirella gen. n. is not highly modified version of the manuscript, their advices and remarks nere stimulat- ing and helpful. Thanks to all the peoplc r-ho worked at the PràL della for scansorial adaptation, as for instance in Vacca site. Thanks are due also to Dr. M. Brunetti (Milano) rvho care- (Peterson 1984) or in drepanosaurids (Renesto 199.ta; b, fully prepared the specimen, and especially to Prof. A. Tintori (Mi- 2000), thus it is feasible that Megachirella gen. n. was not lano) for the field u'ork. This paper is a contribution ol rhe project specialized for arboreal iife, but lived like some extant 'Anisico- Kùhwiesenkopf (Prà della Vacca): paleoecologia e paleocli- semi-arboreal forms, like anolid lizards (Peterson 1971). matologia" supported by the Museo Archeologia e Natura of Bolzano feeding on insects and other invertebrates both on the (Alto Adige) under the leadership of Prof. C. Broglio Loriga from the ground and on trees and branches. Ferrara lJniversity".

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