Rionegrina pozosaladensis igen. et isp. nov. (2 Viewers)

[Fred Ruhe]

Ricardo o N. Melchor, Silverio F. Feola,, M. Cristina Cardonatto, Nahuël Espinoza, Manuel A. Rojas-Manriquez & Lorena Herazo, 2023

First terror bird footprints reveal functionally didactyl posture

Scientific Reports First terror bird footprints reveal functionally didactyl posture - Scientific Reports

Abstract

Terror birds (Aves, Phorusrhacidae) comprise the most outstanding group of South American Cenozoic avifauna, and have been considered dominant predators. Terrestrial habits were inferred using the reduction of their forelimbs and high body mass. Phorusrhacids were considered functionally tridactyl with three relatively short digits II–IV and a small, elevated digit I. The function of the ungual phalanges of digit II have been debated, including the utility of the ungual for retention or stabbing of prey. Incomplete or lack of preservation of foot bones have hampered understanding of the evolution and diversification of Phorusrhacidae. Here we show the first known and well-preserved footprints of Phorusrhacidae with a didactyl posture, which are named Rionegrina pozosaladensis igen. et isp. nov. These footprints yield unprecedented information on the locomotor habits of the group. The finding implies that medium-sized, Late Miocene (~ 8 Ma) phorusrhacids developed strong cursorial adaptations; achieved through reduction of digit II, raised metatarso-phalangeal pad, main body support in a large and thick digit III, and digit IV as outrigger. Raised and long claw of digit II was probably used in pining of prey. Phorusrhacid footprints differ from the Early Cretaceous didactyl footprints of deinonychosaurian dinosaur affinity by its larger size and strong mesaxony.

Enjoy,

Fred

 

[Björn Bergenholtz]

Sorry Fred, but what's (the meaning of): "igen. et isp. nov." ... ?!?

I simply have to ask, as I've never seen those abbreviations before, at least not in a Birding context (even if I do understand that et, and nov. are equal of; and/&, + nova/New, of course).

Is it just a haphazard/unfortunate typo, or typos (twice!?), alt. a copy/paste issue/problem, or something completely different? Possibly connected to Ichnology (the study of traces/fossilized tracks), or?

What have I missed? Please enlighten me (and everyone else).

Björn

PS. Either way, I doubt that Apple (Inc.), or the "iGeneration", have started their own Paleontology Taxonomy, in line with; iPhone, iPad, iBook, etc. ...

 

[l_raty]

Sorry Fred, but what's (the meaning of): "igen. et isp. nov." ... ?!?

Ichnogenus et ichnospecies.
See Ichnotaxon - Wikipedia

 

[Fred Ruhe]

Sorry Fred, but what's (the meaning of): "igen. et isp. nov." ... ?!?

I simply have to ask, as I've never seen those abbreviations before, at least not in a Birding context (even if I do understand that et, and nov. are equal of; and/&, + nova/New, of course).

Is it just a haphazard/unfortunate typo, or typos (twice!?), alt. a copy/paste issue/problem, or something completely different? Possibly connected to Ichnology (the study of traces/fossilized tracks), or?

What have I missed? Please enlighten me (and everyone else).

Björn

PS. Either way, I doubt that Apple (Inc.), or the "iGeneration", have started their own Paleontology Taxonomy, in line with; iPhone, iPad, iBook, etc. ...

Ichnogenus et ichnospecies.
See Ichnotaxon - Wikipedia

In connection to , footprints you talk of ichnogenera anf ochnospecies (and ichnofamiliae, it is a parataxonomy.

When it concerns eggshell you get oofamilia, oogenus and oospecies


Fred

 

[Fred Ruhe]

Systematic ichnology

Ichnogenus Rionegrina igen. nov.
Type ichnospecies Rionegrina pozosaladensis isp. nov.

Diagnosis: Functionally didactyl footprints of moderate to large size (footprint length > 300 mm) composing a bipedal trackway. Footprints markedly mesaxonic with footprint length /width ratio ~ 1.5. Thick, straight, deep and fusiform digit III impression, smaller slightly curved digit IV, and digit II composing a short and shallow elliptical impression. Digit impressions commonly lacking digital pads and not united to a shallow subcircular metatarso-phalangeal pad impression. Well-developed and thick subtriangular claw trace in digit impressions III and IV. Tip of claw imprint II disconnected from digit impression occasionally preserved. Average divarication II–III smaller than III–IV. Narrow trackway (external trackway breadth/footprint width ~ 1.6) with high pace angulation (> 160°), and negative (inward) rotation of footprints. Differs from Velociraptorichnus by a much larger size, marked mesaxony, and separation between digital and metatarso-phalangeal pads. Distinguished from Dromaeopodus by larger III–IV divarication, longer and straight digit III impression, lack of well-defined phalangeal pads, and proportionally smaller metatarso-phalangeal impression. Differences with Dromaeosauripus are a much larger size, presence of a metatarso-phalangeal pad impression, straight digit III impression that is much larger than that of digit IV, and absence of well-marked phalangeal pad imprints.

Etymology: After the Río Negro Province and the homonymous geologic formation, where this ichnogenus occurs.

Remarks: Rionegrina exhibits a set of morphological features that differs from any named ichnotaxa and previously recorded fossil or extant footprint. Comparisons with morphologically similar didactyl ichnogenera are related to Early Cretaceous footprints of dei nonychosaurian (theropod dinosaur) affinity. These includes Velociraptorichnus, Dromaeopodus, and Dromaeosauripus. Velociraptorichnus and Dromaeopodus share a “heel” impression and a reduced impression of digit II, whereas Dromaeosauripus is composed of nearly parallel impressions of digits III and IV, with no “heel” impression. Rionegrina is about 30% larger than the largest specimens of Dromaeopodus (the largest ichnotaxon of deinonychosaurian affinity), display a marked mesaxony whereas the potentially comparable ichnogenera have digit III and IV of similar length. In addition, Rionegrina have large divarication III-IV angle, lack of well-defined phalangeal pads (or a single welldefined digital pad) and have straight digit impressions. Other ichnogenera of purported didactyl theropods are excluded from this comparison: Menglongipus, Paravipus, and Sarmientichnus. Menglongipus is based on material of suboptimal preservation and thus of dubious validity. Paravipus is a Jurassic purported didactyl
ichnogenus that probably represent swim trace fossils. Sarmientichnus is also a Jurassic ichnogenus representing didactyl theropod footprints reflecting particular substrate conditions that was recently considered of deinonychosaurian affinity.

Rionegrina pozosaladensis isp. nov.

Holotype: In situ trackway composed of eleven consecutive footprints (R1 to R6,). Orthomosaic (http:// dx. doi. org/ 10. 6084/ m9. figsh are. 23749 107), digital elevation model (http:// dx. doi. org/ 10. 6084/ m9. figsh are. 23749 260) and interpretative drawing (http:// dx. doi. org/ 10. 6084/ m9. figsh are. 23751 186) of complete trackway. A 3D printing of a left (L1) and right (R2) footprint of the holotype trackway is housed as specimens GHUNLPam 29796 and 29797, at the Colección Paleontológica de la Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa (Santa Rosa, La Pampa, Argentina).

Diagnosis: Only known ichnospecies, same as for the ichnogenus.

Etymology: After the Pozo Salado locality, Río Negro Province, Argentina; where this ichnospecies was found.

Age: Miocene of Argentina, Río Negro Province

Remarks: Three consecutive tridactyl footprints with a moderate reduction of digit II and composing a bipedal trackway has been reported for the unit, and compared with the footprints of large birds (cf. Cariamidae). These are deep undertracks (about 0.15 m deep) of roughly comparable size (340 mm long, 305 mm wide) that are proportionally wider and lack the claw trace of digit III (Fig. 6a, b). This material is considered of dubious affinity and distinct from R. pozosaladensis.

Fred


Fig. 1 Holotype trackway of Rionegrina pozosaladensis igen. et isp. nov. (a–c) Orthomosaic, digital elevation model and interpretative drawing of the holotype. (d,e) Detail of orthomosaic and digital elevation model of fifth right footprint (R5). (f,g) Detail of orthomosaic and digital elevation model of the fourth left footprint (L4). White arrow points to wrinkle traces and black arrows to tip of digit II claw trace. R1-R6: consecutive right footprints, L1–L5: consecutive left footprints, II: digit II.