Origin of the propatagium in birds

Uno and Hirasawa 2023 reported,
“Avian wings as organs for aerial locomotion are furnished with a highly specialized musculoskeletal system compared with the forelimbs of other tetrapod vertebrates. Among the specializations, the propatagium, which accompanies a skeletal muscle spanning between the shoulder and wrist on the leading edge of the wing, represents an evolutionary novelty established at a certain point in the lineage toward crown birds. However, because of the rarity of soft tissue preservation in the fossil record, the evolutionary origin of the avian propatagium has remained elusive.”

Unfortunately the authors never state what the propatagium is used for. Nor do they mention bats or pterosaurs, which both developed a propatagium by convergence.

Peters 2002 reported,
“Prolonged tree-clinging may have contributed to the development of the propatagium and pteroid bone as passive aids to prevent overextension of the elbow—but only if the pterosaur held its torso away from the tree trunk, like a sloth, a flying lemur or a lumberjack, rather than embracing it closely. Brown et al. (1995) showed that a tendon in the leading edge of the propatagium in birds prevents elbow extension due to aerodynamic drag in flight. The origin of this tendon and its associated propatagium may be traced to early Cretaceous birds, such as Confusciusornis (Clarke et al., 2001), which could grapple tree trunks with their wing claws, like a pterosaur.”

The authors do not cite Brown et al 1995.
Nor do they cite Clarke et al 2001.
Nor do they mention ‘over-extension’ or ‘cling’.
They do mention ‘grasping items such as prey’, but a propatagium is not needed for that.

Uno and Hirasawa 2023 continue,
“Here we focus on articulated skeletons in the fossil record to show that angles of elbow joints in fossils are indicators of the propatagium in extant lineages of diapsids (crown birds and non-dinosaurian diapsids), and then use this relationship to narrow down the phylogenetic position acquiring the propatagium to the common ancestor of maniraptorans.”

That’s one way to do it: measuring elbow angles.

“Our analyses support the hypothesis that the preserved propatagium-like soft tissues in non-avian theropod dinosaurs (oviraptorosaurian Caudipteryx and dromaeosaurian Microraptor) are homologous with the avian propatagium, and indicate that all maniraptoran dinosaurs likely possessed the propatagium even before the origin of flight.”

No doubt. Rapid flapping forces make elbows extend. That needs to be limited by a propatagium, both in flight and in non-volant displays.

BTW… The propatagium (with feathers in birds) also adds coverage (shade, weather protection) for eggs in nests, but that aftereffect is also overlooked by the authors.

Figure 2. Cover of the children’s book, ‘Raptors! The nastiest dinosaurs’ by Don Lessem, illustrated by David Peters. Note the propatagium in this 1996 rendition.

“On the other hand, the preserved angles of wrist joints in non-avian theropods are significantly greater than those in birds, suggesting that the avian interlocking wing-folding mechanism involving the ulna and radius had not fully evolved in non-avian theropods.”

Wing folding is a behavior not influenced by a propatagium, which becomes limp and useless when the wings of birds, bats and pterosaurs fold away in storage.

“Our study underscores that the avian wing was acquired through modifications of preexisting structures including the feather and propatagium.”

Unfortunately the authors’ cladogram of propatagium absence and presence is undercut by taxon exclusion.

References
Brown RE, Baumel JJ and Klemm RD 1995. Mechanics of the avian propatagium: flexion-extension mechanism of the avian wing. Journal of Morphology 225, 91–105.
Clarke JA, Gauthier JA, Norell MA and Ji Q 2001. The origin and significance of a propatagium in flying dinosaurs. Journal of Vertebrate Paleontology 21 (Supplement to No. 3), 41A.
Peters D 2001. A New Model for the Evolution of the Pterosaur Wing—with a twist. Historical Biology 15:277–301.
Uno Y and Hirasawa T 2023. Origin of the propatagium in non-avian dinosaurs. Zoological Letters 9(4): https://doi.org/10.1186/s40851-023-00204-x

Two anal fins on Xenacanthus? No.

Short one today.
Popping an old myth.

Xenacanthus is famous for having two anal fins.
Actually that second fin is the lower caudal fin. Homology is the key.

wiki/Xenacanthus

‘Enigmatic’ Protospinax enters the LRT between dogfish and sawfish + skates

Jambura et al 2023
describe an excellent skeleton (PBP-SOL-8007) of the Late Jurassic shark, Protospinax annectans (Woodward 1918-1919, Figs 1, 2).

From the abstract
“since its first description more than 100 years ago, its phylogenetic position within the Elasmobranchii (sharks and rays) has proven controversial, and a closer relationship
between Protospinax and each of the posited superorders (Batomorphii, Squalomorphii, and Galeomorphii) has been proposed over the time.”

By including more taxa and scoring no soft tissue, the large reptile tree (LRT, 2222 taxa, Fig 4) nests Protospinax (Figs 1, 2) between Squalus, the dogfish shark (Fig 5), and Pristis, the sawfish, a taxon basal to guitarfish + skates. Earlier the LRT invalidated the superorder Batomorphii (Batoidea) by splitting traditional members into a variety of distantly related clades.

Figure 1. PBP-SOL-8007 specimen of Protospinax annectans (Woodward 1918) in situ and outline graphic from Jambura et al 2023. Frame two with contrast boost added here.

The Jambura et al abstract continues:
“A data matrix with 224 morphological characters was compiled and analyzed under a
molecular backbone constraint.”

The LRT does not employ molecules. Readers are once again warned against using molecules in phylogenetic analyses because too often they recover untenable tree topologies.

It’s worth noting: in the Jambura et al. cladogram (Fig 3) no taxa are transitional between hybodontid sharks and traditional batoids.

By comparison, the LRT (Fig 4) documents several flattened taxa transitional to several rays and skates.

Figure 2. Skull of PBP-SOL-8007 specimen of Protospinax annectans (Woodward 1918) in dorsal view, in situ, under UV light. First color overlay from Jambura et al 2023. Second color overlay with tetrapod homology colors (Frames 4, 5) added here. Figure 5 indicates mandible elements largely hidden beneath the skull.

The Jambura et al abstract continues:
“the revision of our morphological data matrix within a molecular framework highlights the lack of morphological characters defining certain groups, especially sharks of the order Squaliformes, hampering the phylogenetic resolution of Protospinax annectans with certainty. Furthermore, the monophyly of modern sharks retrieved by molecular studies is only weakly supported by morphological data, stressing the need for more characters to align morphological and molecular studies in the future.”

By contrast, the LRT (Fig 4) completely resolves the Chondrichthyes by including more taxa, including a more primitive outgroup taxon, and avoiding molecular + soft tissue data.

Figure 3. Cladogram from Jambura et al 2023 dividing chondrichthys into traditional clades, including batoids, an invalid clade in the LRT.

Jambura et al report,
“Phylogenetic analyses are the foundation for many evolutionary studies, providing
vital information about evolutionary rates, origination, diversification, and extinction of
certain phylogenetic units of different ranks, and thus contribute to our understanding
of the inherent drivers of biological diversity.”

Agreed.

Figure 4. Subset of the LRT focusing on sharks and their kin with the addition of Protospinax (yellow). Here traditional members of the Batoidea are split apart invalidating that clade.

Unfortunately, Jambura et al concluded,
“For the moment, the phylogenetic position of Protospinax is best regarded as tentative and its use as a calibration fossil for the divergence time of modern sharks and rays is highly questionable until its phylogenetic position can be resolved.”

Colleagues: Please add taxa and avoid molecules, then report results, especially if they differ from the LRT (subset Fig 4), which had no trouble nesting Protospinax.

Figure 5. Skull of Squalus acanthi as with DGS colors added according to tetrapod homologies. Compare to Protospinax skull in figure 2.

Protospinax annectans
(Woodward 1919, Jambura et al 2023, Lower Tithonian, Late Jurassic, 90cm long) is traditionally nested close to angel sharks and some saw sharks, but here nests between Squalus and saw sharks + guitarfish + skates. This appears to be a novel hypothesis of interrelationships. If not, please send a citation so I can promote it here.

References
Jambura PL et al (12 co-authors) 2023. Systematics and Phylogenetic Interrelationships of the Enigmatic Late Jurassic Shark Protospinax annectans Woodward, 1918 with Comments on the Shark–Ray Sister Group Relationship. Diversity:15(311) 1-43.. https:// doi.org/10.3390/d15030311
Woodward AS 1919. On Two New Elasmobranch Fishes (Crossorhinus jurassicus, sp. nov., and Protospinax annectans, gen. et sp. nov.) from the Upper Jurassic Lithographic Stone of Bavaria. Proc. Zool. Soc. Lond. 1919, 13, 231–235.

More information on: Backbone constraint

wiki/Squalus
wiki/Protospinax

Body length estimates for Dunkleosteus

Engelman 2023 reported,
“Large arthrodires (Dunkleosteus, Titanichthys) were much smaller than previously thought and vertebrates likely did not reach sizes of 5 m or greater until the Carboniferous. Lengths of 5–10 m are commonly cited, but these estimates are not based on rigorous statistical analysis. Applying this method to Dunkleosteus terrelli results in much smaller sizes than previous studies: 3.4 m for typical adults (CMNH 5768) with the largest known individuals (CMNH 5936)
reaching ~4.1 m.”

In the large reptile tree (LRT, 2221 taxa) the Late Devonian giant with weak jaws, Titanichthys, is not related to predatory Dunkleosteus (Figs 1, 2) and is not presented in graphic form by Engelman 2023.

Figure 1. Images of Dunkleosteus from Engelman 2023 compared to images of related arthrodires from the literature. Eastmanosteus, like Dunkleosteus, preserves no post-pectoral data. Note how Engelman’s freehand presentation of Amazichthys differs from in situ tracings. This is the key to different length estimates.

Here
graphics (Figs 1, 2) pretty much tell this tale of a tail. Estimates of 4.1 meters for Dunkleosteus appear to be underestimated based on adding the post-pectoral data of tiny Amazichthys to the skull of Dunkleosteus bringing its length back to 5m. Engelman’s use of freehand images (Figs 1, 2) seems to be the reason why his guess of 4.1 m for a maximum length of Dunkleosteus differs from the present estimate. Try to avoid using freehand graphics because freehand departs from raw data

Figure 2. Freehand images from Engelman 2023 compared to scale with images that add the post-pectoral data of Amazichthys to the skull of Dunkleosteus bringing the estimate of length back to 5m. Note how Engelman’s presentation of the ‘largest great white shark’ assumes the proportions of the chubby Dunkleosteus provided with killer whale markings.

Very few arthrodires and related placoderms preserve post-pectoral data.
All that do preserve post-crania are relatively small (Fig 2). So extrapolation is necessary to estimate shape, size and proportions for the post-pectoral estimates of Dunkleosteus. Engelman did this with 57 pages of text and math. That was a great effort, but in the end, both methods amount to estimates.

References
Engelman RK 2023. A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira). Diversity 15: 318, 57pp.

YouTube video on this topic.

Same YouTube link by RK Engelman:
https://www.youtube.com/watch?v=mrATz5jUk2M

My comments on the video:
While it is interesting to examine lampreys, tuna and sharks for comparison, only the closest relatives should be used to imagine the post-crania of Dunkleosteus. Coccosteus was close, but now Amazichthys is closer.

At 15:41 Engelman shows how the length of the chest shield should be equal to the length to the tail base. I tested that hypothesis with calipers on Amazichthys (also shown at 15:41). Amazichthys has a relatively shorter chest shield relative to the rest of the post-crania.

A minute or so later Engelman reports the length to the posterior dorsal shield is likely to be 0.36 the length of the total fish. This is again contradicted by Amazichthys, which has a longer body and shorter dorsal shield.

In any case applying the Bauplan of Amazichthys should have been the preferred method for estimating the still unknown length of the Dunkleosteus post-crania.

Additionally, the shapes of the Amazichthys post-cranial fins appear to have rounded tips, rather than sharp, shark-like tips as in Engelman’s restoration.

The skull of Hippocampus, the sea horse

New data has been recovered
for the skull of Hippocampus, the sea horse (Fig 1), based on Van Wassenbergh et al 2009.

Figure 1. Adult seahorse skull from. Van Wassenbergh et al 2009. Tetrapod homology colors added here.

Previously a neonate skull was employed
by the large reptile tree (LRT, 2221 taxa), which did not include ossified postorbital bones (= circumorbital series). In the adult the postorbital(s) (amber) are all anterior to the orbit.

Figure 2. A series of shrimpfish, including Hippocampus, the seahorse.

Hippocampus heptagonus
(Rafinesque 1810; 4cm in length) is the extant seahorse, a fish that has transformed into a vertically oriented axis with a skull bent down on a sort of neck. Propulsion is slow, mainly from the small transparent dorsal fin.

Figure 3. The giant oarfish, Regalecus glesne, to scale with a couple of swimmers. Often it swims vertically, like a sea horse, propelled by its dorsal fin, often at great depths.Note the elongate pelvic fins.

BTW
the oarfish, Regalescus, (Fig 3) is still a giant sea horse in the LRT, sharing more traits than any competing taxa.

References
Van Wassenbergh S, et al (6 co-authors) 2009. Suction is kid’s play: extremely fast suction in newborn seahorses. Biology Letters 5: 200–203

Ray-fin fish divided by niche

Recent housekeeping
in the ray-fin fish subset of the large reptile tree (LRT, 2221 taxa, Fig 1) plus application of their niche space reveals some interesting patterns.

Figure 1. Subset of the LRT focusing on ray-fin fish. Colors indicate niche spaces. Updated 2.28.23.

Nearly every ray-fin clade
explored several niches, from open seas to sea floors to caves to deep seas, from fast to slow in oceans and fresh water. Tiny taxa are present but do not nest at the base of a majority of clades. More tiny fossil taxa might change this. Time-wise it looks like all the major clades appeared by the Late Jurassic with origins in the Devonian to Carboniferous.

“The function and evolution of the most bizarre theropod manual unguals are [not] revealed”

Qin, Liao, Benton and Rayfield 2023 headline their report,
“Functional space analyses reveal the function and evolution of the most bizarre theropod
manual unguals.” then change their mind when they also report, “the bizarre, huge Therizinosaurus had sickle-like unguals of such length that no mechanical function has been identified.”

Try not to do write click-bait headlines like this. Make sure your text pays off (= fully describes) any promises made by your headline.

Figure 1. A selection of therizinosaurs shown to scale from the authors at Wikipedia. From the start clade members had long, sharp manual unguals.

This is a paper so focused on manual unguals
it fails to include one reconstructed skeleton. Or two. Or eleven (Figs 1–3). Sometimes the answer you and your co-authors seek can be found in the complete Bauplan of the genus and how it compares to other related taxa. So, expand your view if answers to the questions you seek evade your first attempts.

The authors report,
“Therizinosaurians had elongate fingers with slender and sicklelike unguals, sometimes over one metre long.”

“Previous studies have already discussed their bizarre forelimbs, especially their exaggerated sizes when compared to overall body dimensions, strange anatomies, morphological evolution, and some functional simulations using finite element analysis. Therizinosaurians are better understood, and they are assumed to have been giant bipedal, ground sloth-like herbivorous animals5. With reference to the most remarkable elongate sickle-like unguals that emerged in late-branching members, simulation-based research suggested they were most optimal for hook-and-pull functions (defined here as looping the claw tip around and behind an object, then pulling), and possibly also for cutting tree branches.”

Therizinosaurids were herbivores = prey for carnivores. So it is strange that the keywords, ‘defence’ or ‘defense’ are not found in the text.

According to figures 1–3, not all therizinosaurids were giants.

Figure 2. Not shown in figure 1, Falcarius utahensis is a 4m long primitive therizinosaur with large manual unguals. The model skull is largely restored.

Figure 3. Tiny Rahonavis nests with Jianchangosaurus in the LRT. The latter is half the length of Falcarius in figure 2.

The authors also discuss
tiny alvarezsaurids. They report, “Aalvarezsauroids and therizinosaurians are closely related”

The LRT does not support this hypothesis of interrelationships.

“The combined quantitative evidence from shape, function and measurements shows a consistent tendency of morphological specialisation along with scale increase, but according to the general functional performance we test, the Therizinosaurus ungual is a bizarre outlier with very high overall stress distribution, which mean very low functional performance..”

“The extremely enlarged, narrowed and functionally generally useless unguals of Therizinosaurus [Fig 1] might have overgrown in proportion to the already very large body size, just as the huge antlers of Megaloceros giganteus, or some overly complicated frills in late
ceratopsians may have enlarged far beyond functional requirements.”

Sounds like the authors stopped wondering and lost interest in figuring out alternate possibilities for those hyper-elongate manual unguals. Look at the teeth in Jianchangosaurus (Fig 3). It could not defend itself by biting, only by runniing, and if cornered, by slashing.

“The manual unguals of Therizinosaurus have several orders of magnitude higher stress distributions when compared to other therizinosaurian unguals, suggesting they could hardly have functioned in as useful a manner as the other unguals, but more likely were decorative structures. Our functional evidence cannot reject the ecological analogy of Therizinosaurus to giant ground sloths, because it could still feed efficiently by its highly modified jaws, and elongated neck. Therefore, considering their strictly bipedal, purely terrestrial lifestyle and having the largest body size of any theropod dinosaurs, the elongated hand with sickle-like unguals might have been used mostly for threatening enemies or exhibition when mating, by analogy with the otherwise useless wings seen in ostriches.”

If Mike Benton is your co-author (as he is here) and he is the leading professor at your university, problems like this paper tend to pop up. You already known you have to go along to get along, as noted many times over the past decade in this blogpost. On the plus side, Benton’s influence over at Nature does get work published.

Bottom line: If you’re looking to make paleo headlines,
and a chat with a journalist or two, even if your results are dim, always supply your headline with a superlative, like ‘most bizarre’.

References
Qin Z, Ko C-C, Benton MJ and Rayfield EJ 2023. Functional space analyses reveal the function and evolution of the most bizarre theropod manual unguals. Nature Communications Biology. https://doi.org/10.1038/s42003-023-04552-4

Phylogenomics vs genomics 2023

Callender-Crowe and Sansom 2023 tested
bones, soft tissues and genes, then reported bones are more congruent with genes than soft tissue.

Unfortunately the authors are living under the widespread illusion that gene results always provide more accurate results than trait results. This idea is true – except in paleontology and deep time systematics – as noted many times earlier (also see Fig 1).

Figure 1. Which taxa share more traits? Phoenicopterus, the flamingo, nests with Cariama, the seriema, in the LRT. By contrast, the flamingo nests with Gavia in the Prum et al 2015. DNA study. No one noticed those results are untenable.

From the abstract
“Despite increased use of genomic data in phylogenetics, morphological information remains vital for resolving evolutionary relationships, particularly for fossil taxa.”

So why would paleontologists ever embrace untenable gene studies?

“The properties and models of evolution of molecular sequence data are well characterized and mature, relative to those of morphological data.”

This is a widespread belief, as indicate by that statement. However, the large reptile tree (LRT, 2122 taxa) does not support that widespread belief.

“Furthermore, heterogeneity, integration and relative homoplasy of empirical morphological data could prove problematic for phylogenetic reconstruction.”

“Could prove”. See how they phrase it? Wrapping their concern in a contingency? This sounds like the authors have not tested traits vs genes, and are reticent to do so.

“Here we compare osteological and non-osteological characters of 28 morphological datasets of extant saurians in terms of their homoplasy relative to molecular trees.”

Read between the lines. This means the authors are giving molecular trees the gold standard, rather than the other way around. The LRT indicates this is incorrect thinking.

“Analysis of individual avian datasets finds osteological characters to be significantly more consistent with molecular data than soft characters are.”

So what? What we’re looking to do is to model actual evolutionary events in deep time. This can only be done with fossils. Ignore fossils = taxon exclusion.

“Significant differences between morphological partitions were also observed in the age at which characters resolved on molecular trees. Osteological character changes occur relatively earlier in deep branches, whilst soft-tissue character transitions are more recent in shallow branches.”

The authors are using the wrong standard.

“The combined results demonstrate differences in evolutionary dynamics between morphological partitions. This may reflect evolutionary constraints acting on osteological characters, compared with the relative lability of soft characters.”

The authors are guessing. They need to build their own LRT to determine interrelationships while minimizing taxon exclusion. Then they will see that genes too often deliver untenable results (Fig 1).

“Furthermore, it provides some support to phylogenetic interpretations of fossil data, including dinosaurs, which are predominately osteological. Recent advances in amphibian and mammal phylogenetics may make these patterns possible to test for all tetrapods.”

Some support? We need results that provide complete support. The LRT provides that support using trait analysis that documents convergence = homoplasy.

References
Callender-Crowe LM and Sansom RS 2023. Osteological characters of birds and reptiles are more congruent with molecular phylogenies than soft characters are. Zoological Journal of the Linnean Society 194:1–13.

Hamipterus pectoral complex

Preface:
All I’ve seen, so far, is this abstract. Send a PDF if you have one.

From the Wu et al 2023 abstract:
“As one of the mysteries volant vertebrates, pterosaurs were completely extinct in the K-Pg extinction event, which hampered our understanding of their flight. Recent studies on pterosaur flight usually use birds as analogies, since their shoulder girdle share many features. However, it was also proposed that these two groups may differ in some critical flight mechanisms, such as the primary muscles for the upstroke of the wings. Here, we describe and characterize the detail features of the pectoral girdle morphology and histology in Hamipterus from the Early Cretaceous of Northwest China for the first time. Our research reveals that the scapula and coracoid of Hamipterus form a synostosis joint, representing a distinct pectoral girdle adaption during pterosaur flight evolution, different from that of birds.”

Good to know, but that’s not surprising. “synostosis joint” = fused. Placed into a phylogenetic context, pterosaurs are lepidosaurs. Birds are archosaurs. Their elements should be different.

“The residual of the articular cartilage of the glenoid fossa supports the potential for cartilage tissue preservation in this location. The morphology of the acrocoracoid process of Hamipterus indicates it may work as a pulley for M. supracoracoideus as the main power of flight upstroke resembles that of birds. But the saddle type of the shoulder joint of the pterosaur may limit the rotation of the humerus head, suggesting a particular mechanism to control the angle of attack unlike birds.”

Play with uncrushed bones to find out.

“The presence of both the similarity and differences between the flight apparatus of pterosaurs and birds are highlighted in our research, which may be related to the flight mechanism and forelimb functional adaption. The distinctive feature of the flight apparatus of pterosaur should be treated with caution in future research, to better understand the life of this unique extinct volant vertebrate.”

So, the authors are not saying much.

Figure 1. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex, a term not mentioned by the authors.

The term, ‘sternal complex’
is not mentioned in the abstract.

References
Wu et al (5 co-authors) 2023. The morphology and histology of the pectoral girdle of Hamipterus (Pterosauria), from the Early Cretaceous of Northwest China. The Anatomical Record Special Issue. https://doi.org/10.1002/ar.25167

Extant Galaxias now nests with Middle Triassic Prohalecites in the LRT

Recent housekeeping
in the large reptile tree (LRT, 2221 taxa) moves extant Galaxias (common name: Inanga, or common galaxias, Fig 1) close to tiny Middle Triassic Prohalecites (Fig 1).

Figure 1. Extant Galaxias and Middle Triassic Prohalecites now nest together in the LRT. One helps decipher the other. Both have a heterocercal tail, based on the caudal skeleton.

These are both basal ray fin fish in the LRT.
Only the extant anchovy (Engraulis) is more primitive and extant in the clade of ray-fin fish.

Prohalecites porroi
(Bellott 1857, Tintori 1990, MCSNIO P 348, Middle Triassic; 4cm) is a late surviving basal bony ray-fin fish (Actinopterygia, Osteichthyes). No trace of scales is preserved in any specimen. No neurocranial material is preserved. Tintori left Prohalecites as a Neopterygian incertae sedis, “because its characters do not perfectly fit in any of these cited groups.” Hemichordacentra are present. The preopercular is so slender it is rodlike.

Galxias attenuatus
(= Galaxias maculatus Cuvier 1816, 4–58cm depending on species, typically 10cm) is the Inanga, or common galaxias, an extant freshwater fish. It spends the first six months at sea.

Jonathan Chang, author of The Fish Tree of Life
also nests Prohalecites with Galaxias and many other taxa.

References
Arratia G and Tintori A 1999. The caudal skeleton of the Triassic actinopterygian †Prohalecites and its phylogenetic position, p. 121–142. In: Mesozoic Fishes 2—Systematics and Fossil Record. G. Arratia and H.-P. Schultze (eds.). Verlag Dr. F. Pfeil, München.
Arratia G 2015. Complexities of early Teleostei and the evolution of particular morphological structures through time. Copeia 103(4):999–1025.
Bellotti C 1857. Descizione di alcune nuove specie di pesci fossili di Perledo e di altre localtta lombarde. 419–432. In Sopani A (ed) Studi geologici sulla Lomabardia. Editore Turati, Milano.
Tintori A 1990. The actinopterygian fish Prohalecites from the Triassic of northern Italy. Palaeontology 33:155–174.

wiki/Prohalecites
wiki/Galaxias
https://fishtreeoflife.org/fossils/galaxias-effusus/