Fig 1.
Austrian map with stratigraphic and lithological overview and positions of layers (red asterisks) comprising the here described black carbonized fossils.
Black asterisk with P: position of the Konservat-Lagerstätte Polzberg (= Schindelberggraben ravine, Polzberg locality) near Lunz am See. Black asterisk with C: Cave del Predil, Italy comprising also deposits with enigmatic black fossils. (A) Vertical section (middle part) of Polzberg locality. Black asterisk marks position within the stratigraphic scale. Scale bar 20 cm. (B) Enigmatic carbonized structure from Polzberg locality, NHMW 2021/0001/0002. Scale bar 1 cm.
Fig 2.
Belemnoid fossils from the late Triassic Konservat-Lagerstätte Polzberg near Lunz am See.
(A) Hook morphology in phragmoteuthid arm crowns. (B) Semi in situ preserved arm crown. Each arm comprises two rows of hook armory. Terms adapted from [30]. (C) Belemnoid fossil remains, assigned to the taxon Phragmoteuthis bisinuata with its characteristic fan-shaped three-parted proostracum. White arrows pointing to position of carbonized structure.
Fig 3.
Specimens of Type A and Type B fossils from the Polzberg Konservat-Lagerstätte.
(A) Suggested orientation for Type A fossils showing characteristic, curved C structure with prolonged processus. (B) Most complete specimen (NHMW 2021/0123/0057) showing symmetrical, semi-in situ configuration of the structures with likewise in situ preserved hooks, starting in the area of the long dorsal processus above the C structure. (C) Suggested orientation for Type B fossils showing a curved hook-like structure. (D) Cartilaginous structure associated with belemnoid hooks, NHMW 2021/0124/0003a, b. All scale bars 1 cm. ac arm cartilage, cc cephalic cartilage, cr carrier, oc ocular cartilage, h coleoid hooks, ac arm-cartilage structures, pr processus.
Fig 4.
Different views of Type A (possible cephalic cartilage) and B specimens.
(A) Standard "lateral" view of Type A fossils (NHMW 2012/0117/0001) with groove, characteristic processus on prominent C structure. (B) Supposed »cranial« view of Type A specimen (NHMW 2012/0117/0025) with associated wing-elements and in situ preserved hooks. (C) Two Type B fossils with a triangular base and two additional elongated elements (NHMW 2021/0124/0002). (D) Historical specimen from the Geological Survey Austria (GBA 2006/011/0041) from the Rinngraben ravine near Cave del Predil (Raibl, Italy). These specimens show a thicker and more prominent upper part of the C structure. cc cephalic cartilage, cr carrier, h belemnoid hooks, ac arm-cartilage, oc ocular cartilage, pr processus. All scale bars 1 cm.
Fig 5.
Analyses carried out on specimen NHMW 2012/0117/0024.
(A) Thin-section of enigmatic black fossil reveals a widely distributed channel system (grey); red arrows: surrounding calcitic seam/layer. Note the curving of sediment around the fossil specimen. (B) Magnification showing pore space in the center of the fossil. (C) Red arrows mark the outer seam surrounding the fossil. (D) Diagenetic cracks in the black fossil structure. All scale bars 200 μm, except scale bar for A 500 μm.
Fig 6.
Microprobe analysis reveals the elemental distribution near the sediment-fossil boundary.
(A) Composite image of elements in thin-section of specimen NHMW 2012/0117/0024. Aluminium, silicon and oxygen are the main sediment constituents. (B) Carbon is the dominant element in the black fossil structure. (C) Calcite-filled channels and the fossil surrounding calcitic seam/layer. (D) Distribution of sulfur in the sediment corresponds to pyrite nodules. Note the outer dark layer of the fossil, lacking sulfur. All scale bars 100 μm.
Fig 7.
EDS-SEM images of the ultrastructure of specimen NHMW 2012/0117/0024.
(A) Distinct boundary between fine calcareous host rock (hr) and carbonized, amorphous fossil (c). (B) Thin calcareous fossil-surrounding seam/layer (cs, approx. 20 μm thick). (C) EDX-SEM of amorphous structure with calcitic channel fillings. (D) Calcite-filled channel (magnification x 5000; scale bar 10 μm). hr host rock, c carbonized cartilage, ch calcitic channel fillings, cs calcareous fossil-surrounding seam. Scale bar except (D) 100 μm.
Fig 8.
Homologization of fossil specimens with modern coleoid cartilage.
(A) MRT-data [46] of Sepia officinalis. Note the hook-like ending and angle to the C structure. Scale bar 20 mm. (B) 2D-Drawing of cartilage, redrawn magnified from a, showing principal shape of the structure in S. officinalis. Scale bar 2 cm. (C) Digital drawing of most entire specimen (NHMW 2021/0123/0057) obtained during excavations in 2021, with suggested elements as labeled: ac arm cartilage, cc cephalic cartilage, cr carrier, h hooks, oc ocular cartilage, pr processus, st statocysts. Scale bar 1 cm.