Perumegabalanus calziai gen. et sp. nov., a new intertidal megabalanine barnacle from the early Miocene of Peru

Abstract

Living members of the tribe Austromegabalanini are large balanid barnacles (Crustacea: Cirripedia: Neobalanoformes) that live in temperate and cold waters of the Southern Hemisphere. During the Neogene, however, the austromegabalanines also inhabited the Northern Hemisphere, as well as some low- latitude tropical environments. This paper describes a new taxon of austromegab-alanines, Perumegabalanus calziai gen. et sp. nov., from the shallow-marine, nearshore, lower Miocene (19 to 17 Ma, Burdigalian) deposits of the Chilcatay Formation (East Pisco Basin, southern Peru). Among austromegabalanines, this new taxon is characterised by the presence of thick, ornamented, multitubiferous parietes, where the parietal tubes are irregularly partitioned by auxiliary sep - ta; in addition, the sheath is vesicular. Based on morphofunctional considerations, the peculiar shell architecture of P. calziai is here interpreted as well-suited for an existence in the intertidal zone. In the Chilcatay strata, two taxa of Austromegabalanini (i. e., Austromegabalanus carrioli and P. calziai) coexist, representing some of the geologically oldest records of austromegabalanines worldwide – an observation that strongly supports the hypothesis of a circum-equatorial origin and early diversification for this successful lineage of acorn barnacles.

Lower Miocene (Burdigalian) acorn barnacles (Cirripedia: Sessilia) from the Chilcatay Formation of southern Peru: palaeoenvironmental, palaeobiogeographical and evolutionary significance

“…We are grateful to Giovanni Bianucci, Claudio Di Celma, Elisa Malinverno, and Mario Urbina. The results and intrepretations reported herein have been published in an unabridged way by Coletti et al (2018Coletti et al ( , 2019, Di Collareta et al (2019). Coletti et al (2018).…”

“…As with the extant Peruvian species Austromegabalanus psittacus, A. carrioli inhabited very shallow-water littoral and subtidal shelf settings; however, differing from all extant and most extinct austromegabalanines, A. carrioli inhabited a warm-temperate environment. Another taxon of austromegabalanines, Perumegabalanus calziai, is characterised by the presence of thick, ornamented, multitubiferous parietes, where the parietal tubes are irregularly partitioned by auxiliary septa, and by a vesicular sheath (Coletti et al, 2019) (Fig. 1D-F).…”

Taphonomy of a Panopea Ménard de la Groye, 1807 shell bed from the Pisco Formation (Miocene, Peru)

“…Buckeridge 2015). The two formally named Miocene members of Austromegabalanini of the East Pisco Basin, to which the reported specimens are closely related, are interpreted as intertidal and shallow subtidal organisms (Coletti et al 2019;Collareta et al 2019).…”

“…These units are characterized by transgressive, deepening-upward facies associations, recording deposition in shoreface and offshore settings. Careful correlation between different outcrops and accurate dating by means of diatom biostratigraphy, 39 Ar-40 Ar chronology, and strontium isotope stratigraphy Bosio et al 2019Bosio et al , 2020a constrain the deposition of these three unconformity-bounded units: P0 was deposited during the Langhian-Serravallian (c. 14.8-12.4 Ma), P1 during the Tortonian (c. 9.5-8.6 Ma), and P2 during the Tortonian-Messinian (c. 8.4-6.7 Ma). The timing of deposition of these sequences may have been driven by eustatic sea-level variations (Di Celma et al 2018a).…”

“…The same specimen partly preserves the impressions of the terga and scuta, lying appressed to the sheath. The large size of the preserved specimens, their overall shell structure, and especially the observation of a peculiar denticulation pattern of the sutural surfaces of the radii, allowed us to identify them as members of Austromegabalanini (Newman 1979; Buckeridge 2015), a tribe of megabalanine balanids that is known from the Miocene deposits of southern Peru, where at least three species occur (Coletti et al 2018(Coletti et al , 2019Collareta et al 2019).…”