«NATURA BRESCIANA. Ann. Mus. Civ. Sc. Nat.. Brescia, MONOGRAFIA N. 25, 2001: 45-50 TETRAPOD FOOTPRINTS FROM THE LOWER PERMIAN OF WESTERN OROBIC BASIN (N. ITALY) UMBERTO NICOSIA l, AUSONIO RONCHI ' and GIUSEPPE SANTI Key ~vords - fooiprints; Permian; Southern Alps; stratigraphy. Ah.strcrct - Large numbers of tetrapod footprints havc recently been discovercd within sedimcnts pertaining to the Early Perm- ian Collio Fm. in the Western Orobic Basin (between thc iipper Varionc and upper Gerola valleys. Lombardy, Italy). They can bc ascribed to the following taxa: Arnphistri~ropr~s Itr- tirs Haubold, 1970, A. immirirrtrr.~ Haubold, 1970. Dmrnopus Iu- certoides (Geinitz. 1861) and Vrrrrrnop~rs cirri)icinch/~i.s (Mood- ie, 1929). This low-diversity ichnoassociation is coeval with those of Cen- tra1 Eiirope and North America and can also bc correlated with that yielded from the lower portion of the Brescian Colli» Fm. The geological setting as well as the stratigraphic position of the track-bearing sequence is outlined below, togcther with a dis- cussion of some hypotheses for ihe preseiice of this low-diversi- ty ichnoassociation. Purole chiave - impronte; Permiano: Sudalpino; Stratigrafia. Riasslrnto - Un gran numero di impronte di tetrapodi è stato rin- venuto recentemente in terreni appartenenti alla sommità strati- grafica della Formazione di Collio (Permiano inferiore) ncl baci- no Orobico occidentale (tra I'Alta Val Varronc e l'Alta Val Gero- la. Lombardia, Italia). Si tratta delle seguenti icnospccie: Arn- phi.c.cr~iropr~s ILI~LIS Haubold, 1970. A. iwirninutus Haubold. 1970, Drornopirs 1acertoicle.s (Geinitz, 1861 ) e Varar~ol~us curiliriochlus (Moodie, 1929). Questa icnoassociazione, caratterizzata da una bassa diversiti. è coeva con le associazioni del Permiano inferi- ore dell'Europa Centrale e del Nord America e può inoltre essere correlata con quella rinvenuta nella paste inferiore dclla For- mazione di Collio, nell'omonimo bacino triumplino. Oltre all'in- quadramento geologico C stratigrafico della successione di terreni che ha fornito tali impronte, vengono di seguito discusse varie ipotcsi sulle possibili cause di tale ristretta icnoassociazione. MTRODUCTION AND GEOLOGICAL SETTING Late Palaeozoic tetrapod footprints from sediments crop- ping oiit both in the Lower Permian of the centra1 Southern Alps and in the Upper Permian of the Dolomites have been known since the late 19th century (see Conti et al., 1991, fora historical review). Recently, numerous tetrapod footprints have been found in the Permian deposits of the Western Orobic Prealps (up- per Gerola-Inferno and Varrone valleys, Lombardy, Italy) (Fig. I). The footpiints come from the uppermost levels of the local Collio Fm. and have been ascribed to Amphisnuroplrs lcrtlis Haubold, 1970, A. imrniniirus Haubold, 1970, Dro- similar and coeval Early Permian association of Centra1 Europe and North America. The first to report the presence of tetrapod footprints, but on the eastern side of the Orobic Basin (eastern Brem- bana Valley) was Dozy (1935). who ascribed these forms to Aiihotnoicnium orohici~in and Onychicriium escheri. The first of them was later attributed to an extramorphological imprint of Botrachichnus snlninnndroides (Haubold, 1996), while the other taxon was considered as incertae sedis (?Actihates) (Haubold, 197 1). Many years after, Casati & Gnaccolini (1967) and Casati & Forcella (1988) reported scarce findings of some tetrapod footprints in the area close to Rifugio Falc and Piz- zo Varrone. rnopiu lacertoides (Geinitz, 186 1) and Vnranopus curili- Concerning the geology and stratigraphy of the area, the d~~chllu (Moodie, 1929) (Plate 1 and Fig. 3). first detailed studies were undertaken by Porro (1931, This association is closely comparable to a similar one 1932);subsequently, De Sitter & De Sitter-Koornans (1949 recorded in the lower portion of the Collio Fm. cropping and references therein) published a wide geologica1 map of out within the Collio Basin in the Brescia region. and to the the Bergamo Alps, putting together the contributions and 'Dipartinientodi Scienze della Terra, Uiiiversità "La Sapienza". P.le A. Moro 5,001 85 Roma, 1t:ily. 'Dipartimento di Scicnze della Terra, Università di Pavia, Via Ferrata 1, 27 100 Pavia, Italy.