The European eel is a barracuda sister

Earlier we looked at
the moray eel and the electric eel.

Today the European eel,
(Anguilla anguilla) enters the large reptile tree (LRT, 1510 taxa) alongside the barracuda, Sphyraena. Phylogenetically they are some distance away from the electric eel (Electrophorus) and the moray eel (Gymnothorax).

Figure 1. The European eel, Anguilla anguilla in vivo.

Figure 1. The European eel, Anguilla anguilla in vivo.

Figure 3. The skull of Anguilla from xx, with bones colored here and matched to an invivo photo.

Figure 2. The skull of Anguilla from Gregory 1936, with bones colored here and matched to an invivo photo. The traits shown here are closest to a tested barracuda. The lack of tiny circumorbital bones is shared with the related Northern pike, a freshwater barracuda.

Anguilla anguilla (Linneaus 1758; up to 80cm in length, 1.5 exceptionally) is the extant European eel, a sister to the barracuda in the LRT. It lacks pelvic fins and the tail has reverted to a straight tail. The life cycle includes breeding and young hatching in the mid-Atlantic with migration back to European rivers before the adults return to the mid-Atlantic. Anguilla lacks the circumorbital bones, traits shared with the Northern Pike, Esox. Bones are relabeled here based on sister taxa. Note the premaxillae do not meet medially. The vomer is the anteriormost bone.

Figure 1. The skull of the barracuda (genus: Sphyraena) with bones identified with colors.

Figure 3. The skull of the barracuda (genus: Sphyraena) with bones identified with colors.

Figure 2. Skull of the electric eel (Electrophorus). Compare to the halibut in figure 1.

Figure 5. Skull of the electric eel (Electrophorus) distinct from the moray eel (Fig. 4) and European eel (Fig. 2).

Figure 2. The skull of the moray eel, Gymnothorax, in 3 views. Colors added as homologs to tetrapod skull bones. The nares exit is above the eyes.

Figure 4. The skull of the moray eel, Gymnothorax, in 3 views. Colors added as homologs to tetrapod skull bones. The nares exit is above the eyes.


References
Gregory WK 1933. Fish skulls. A study of the evolution of natural mechanisms. The American Philosophical Society 23(2). Reprinted 1959, Eric Lundberg, Laurel FL, Noble offset printers, Inc. New York
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

wiki/European_eel

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The weird ratfish, Iniopteryx, enters the LRT

Distinct from all other tested taxa,
Iniopteryx (Fig. 1) and kin extend their pectoral fins from the dorsal region where they ceased working as fins and began working as fancy secondary sexual traits (Fig. 2). This is similar, but different than a sister chimaera, Falcatus (Fig. 3), famous for its lone long horn.

Figure 1. Skull of Iniopteryx in situ and reconstructed.

Figure 1. Skull of Iniopteryx in situ from Zangrel and Case 1973 (above) and reconstructed (below) using DGS techniques.

Zangrel and Case 1973
introduced us to a new clade of ratfish the named the Iniopterygia (= Iniopterygiformes). All four had a similar body plan, differing mainly in the decorations. Wikipedia reports, “The closest modern-day relatives of the Iniopterygii are the Chimaeras (Chimaeriformes).” In the large reptile tree (LRT, 1505 taxa) Iniopteryx nests within the Chimaeriformes, not as a sister taxon.

Evidently no one yet
has traced the skull bones of these crushed Late Carboniferous taxa, except as broad skull outlines (Fig. 2). Here (Fig. 1) that problem is resolved.

Figure 2.I The Iniopterygidae include Iniopteryx, Promexyele, Iniopera and Sibyrhynchus. These reconstructions are from Zangerl and Case 1973 and the captions label them "tentative."

Figure 2.I The Iniopterygidae include Iniopteryx, Promexyele, Iniopera and Sibyrhynchus. These reconstructions are from Zangerl and Case 1973 and the captions label them “tentative.” Note that none of the skulls include details.

A sister in the LRT
is Falcatus (Fig. 3), which also has a dorsal secondary sexual trait and a skull morphology similar to that in Iniopteryx. Normal pectoral fins emerging from the chest area are present in Falcatus and all other vertebrates with fins/limbs.

Figure 1. The skull of Falcatus with DGS tracing above.

Figure 3. The skull of Falcatus with DGS tracing above.

Chimaera are bottom dwellers,
and sometimes ‘the bottoms’ are very deep. Their eyes are large to pick up the rare photons that make it to those inky depths from above, or are produced by self-illuminated benthic organisms.

Figure x. Subset of the LRT focusing on fish and other basal vertebrates.

Figure x. Subset of the LRT focusing on fish and other basal vertebrates.


References
Zangerl R and Case GR 1973. Iniopterygia : a new order of Chondrichthyan fishes from the Pennsylvanian of North America. University of Illinois Urbana-Champaign. Chicago : Field Museum of Natural History.

wiki/Iniopteryx
wiki/Iniopterygiformes
wiki/Holocephali

Ischnacanthus: basal to spiny sharks and most ray-fin fish

There is a growing consensus
among paleoichthyologists (fish workers) that spiny sharks (clade: Acanthodii) belong closer to bony ray-fin fish, rather than to sharks. The large reptile tree (LRT, 1504 taxa; subset Fig. 1) has been nesting spiny sharks between lobe-fin fish and ray-fin fish since pertinent fish taxa have been added many months ago. That hypothesis of relationships is novel and continues today, even after a few dozen taxa have been added inviting spiny sharks to nest elsewhere.

Figure 1. Subset of the LRT focusing on the clade of free-swimming lobefin fish that gave rise to acanthodians (spiny sharks) and ray fin fish.

Figure 1. Subset of the LRT focusing on the clade of free-swimming lobefin fish that gave rise to acanthodians (spiny sharks) and ray fin fish. Note: some acanthodians revert to a ray fin morphology.

Today a basal spiny shark, Ischnacanthus,
(Figs. 1, 2) nests at the base of the spiny sharks, a clade that nests between the semi-lobe-fin, Cheirolepis, and the Jurassic ray-fin pre-piranha, Dapedium, .

Figure 1. Ischnacanthus in situ. Note the tail is right side up here, the torso is ventrally exposed and the skull is upside down (relative to the tail). So this fossil is twisted.

Figure 1. Ischnacanthus in situ. Note the tail is right side up here, the torso is ventrally exposed and the skull is upside down (relative to the tail). So this fossil is twisted. One pectoral spine is split at the root. 

The Ischnacnathus specimen under study
(Figs. 1) is crushed, articulated, and twisted like a wet towel, so, it’s a perfect specimen to apply DGS (color tracing and reconstruction, Fig. 2) methods. Scoring from the reconstruction nests Ischnacanthus conventionally at the base of the Acanthodii in the LRT. Note: several small (vestigial) rays succeed the large pectoral spine. The skull reconstruction greatly resembles that of Cheirolepis, the outgroup taxon and the traditional basal ray-fin fish, despite the presence of a transitional pectoral lobefin.

Figure 2. Ischnacanthus skull in situ and reconstructed. Note the remnants of ray fins posterior to the large pectoral spine.

Figure 2. Ischnacanthus skull in situ and reconstructed. Note the remnants of ray fins posterior to the large pectoral spine. The ventral squamosal is displaced over the maxilla. The circumorbital bones could be confused with a sclerotic ring. Some interesting tooth-like projections emerge from the dorsal squamosal and ventral mandible.

At this point
it is worthwhile to take a look back the Triassic flying fish, Thoracopterus (Figs. 3, 4), which was presented earlier here. In the LRT Thoracopterus is a spiny shark (clade: Acanthodii) only this time with spectacular ray fins.

Figure 1. Thoracopterus is a Triassic flying fish unrelated to extant flying fish, but a sister to giant Xiphactinus.

Figure 3. Thoracopterus is a Triassic flying fish unrelated to extant flying fish, but a sister to giant Xiphactinus.

Be careful not to pull a Larry Martin here!
Just because Thoracopterus has ray fins does not mean it is a member of the ray-fin clade Teleostei. We’ve learned not to depend on one or a dozen traits. Use hundreds of traits and let the software decide where taxa nest. It is also a good idea to create a reconstruction from precise color tracings. Bones can be displaced. Freehand reconstructions introduce bias. You may draw what you think a taxon should be, and that’s never the way to go.

FIgure 2. Thoracopterus skull colorized from Tintori and Sassi 1992. Tetrapod nomenclature added.

FIgure 4. Thoracopterus skull colorized from Tintori and Sassi 1992. Tetrapod nomenclature added.

Ischnacanthus gracilis (Egerton 1861; Early Devonian, 430 mya; up to 2m in length) is a basal acanthodian with teeth (some spiny sharks are toothless). Traces of ray fins can still be seen posterior to the large pectoral spine. Note the in situ skull is twisted 180º from the tail. Ischnacanthus further cements the nesting of spiny sharks between lobe fins and most ray fins.


References
Egerton P de MG 1860. Report of the British Association for Science for 1859.
Transactions of the Sections. 116.

wiki/Acanthodii
wiki/Doliodus
wiki/Thoracopterus
wiki/Xiphactinus
wiki/Ischnacanthus

Belantsea, an odd Early Carboniferous ratfish

Earlier we looked at Falcatus, an Early Carboniferous ratfish with a diphycercal tail, like that of a teleost. Today, we look at another ratfish with a derived body plan, Belantsea (Figs. 1,2) as it enters the large reptile tree (LRT, 1500 taxa).

Figure 1. Belantsea from Lund 1989 (black and white) and from Long 1995, where the liver was interpreted as a pectoral fin (color).

Figure 1. Belantsea from Lund 1989 (black and white) and from Long 1995, where the liver was misinterpreted as a pectoral fin (color). Be careful of the red one where the artist made a mistake on the liver.

Due to the anterior migration of the jaw joint
and several other traits, Belantsea nests with Chimaera, rather than Falcatus, with which it shares a diphycercal tail. I would not call Belantsea ‘transitional’ between the two morphologies because it has evolved away from that unknown or untested last common ancestor. Due to the small number of ratfish in the LRT, at present it is transitional.

FIgure 1. Belantsea in situ with DGS methods used to identify skull bones and a vestigial anal fin, as in Falcatus (Fig. 3). The premaxillalry beak is similar to the one in Chimaera (Fig. 4).

FIgure 1. Belantsea in situ with DGS methods used to identify skull bones and a vestigial anal fin, as in Falcatus (Fig. 3). The premaxillalry beak is similar to the one in Chimaera (Fig. 4).

Using the pectoral fins for propulsion
is what modern ratfish do, a trait pioneered by a more primitive sister to Belantsea, a ratfish with the look and proportions of a frogfish.

Figure 2. Falcatus traced with DGS methods with reconstructed freehand image applied from xxx.

Figure 3. Falcatus traced with DGS methods with reconstructed freehand image. Note the vestigial anal fin beneath the large tail fin.

Technical note:
MacClade tells me I can no longer add more taxa, now that I have reached the 1500 mark. No worries. Now that the structure is firm, smaller clades can be tested on their own.


References
Long JA 1995. The rise of fishes. The Johns Hopkins University Press, Baltimore and London.
Lund R 1989. New petalodonts (Chondrichthyes) from the Uppper Mississippian Bear Gulch limestone (Namurian E2b) of Montana. Journal of Vertebrate Paleontology 9(3):350–369.

Lophias, the goosefish, enters to LRT

… and not surprisingly
Lophias is a sister to two other bottom dwellers, Electrophorus (the electric eel) and Hippoglossus (the halibut) in the large reptile tree (LRT, 1500 taxa; subset Fig. 5).

Figure 1. Lophias in vivo. The pelvic fins are hidden from view beneath the large pectoral fins.

Figure 1. Lophias in vivo. The pelvic fins are hidden from view beneath the large pectoral fins. So Lophias is all mouth and tail. Inset shows a larva/hatchling not to scale.

The Lophias skull
has more space than bone (Fig. 2) and its flexibility, morphing from flat to wide open, sucks in small prey swimming too close to that wicked toothy gaping mouth. Like its sisters, many cheek bones are absent or greatly reduced in this taxon. Atypical for fish, the intertemporal contacts the tabular and the supratemporal rims both laterally. I think the vomers have the longest teeth, and they are rotated toward the throat… unless the premaxilla has two rows of teeth… which seems less likely.

Figure 2. The flexible Lophias skull can flatten or expand, sucking in small fish and other prey items.

Figure 2. The flexible Lophias skull can flatten or expand, sucking in small fish and other prey items. The prefrontal and most cheek bones are missing here. If those are vomers, those are the largest teeth in the jaws. Otherwise the premaxillae have two rows of teeth.

Lophias americanus (Rafinesque 1810; up to 1.5m in length) is the extant goosefish or monkfish. The closest relative in the LRT is the electric eel, Electrophorus (Fig. 3). The pelvic fins are small and anteroventral to the pectoral fins.

Figure 2. Skull of the electric eel (Electrophorus). Compare to the halibut in figure 1.

Figure 3. Skull of the electric eel (Electrophorus). Compare to Lophias (Fig. 2).

So far,
every additional fish taxon simply drops into place, rather than pushing taxa into other nodes. That means a good way to build a cladogram is a taxon at a time.

Figure 4. Electrophorus, the electric eel, in vivo.

Figure 4. Electrophorus, the electric eel, in vivo.

Figure x. Subset of the LRT focusing on fish and other basal vertebrates.

Figure x. Subset of the LRT focusing on fish and other basal vertebrates.


References
Rafinesque CS 1810. Caratteri di alcuni nuovi generi e nuove specie di animali e piante della sicilia, con varie osservazioni sopra i medisimi. Per le stampe di Sanfilippo: Palermo, Italy. pp. 105, 20 fold. Pl., online

wiki/Goosefish
wiki/Lophius
wiki/Lophius_americanus

The shark-like pre-sturgeon, Chondrosteus, enters the LRT

The nesting of Chondrosteus with sturgeons
is not controversial.

However,
the nesting the traditional ‘bony fish’ Chondrosteus and sturgeons with sharks and ratfish is heretical and documents only part of the evidence for a multiple genesis of bony fish. In the large reptile tree (LRT, 1499 taxa) Chondrosteus (Fig. 1) nests as a shark-like sturgeon from the Early Jurassic, at which time it was a late survivor of a much earlier (likely Silurian), genesis and radiation.

Chondrosteus and sturgeons share a last common ancestor
in the shark-like Cladoselache, which we looked at earlier here.

Figure 1. Chondrosteus skull reconstructed, skull in ventral view in situ and skeleton.

Figure 1. Chondrosteus skull reconstructed, skull in ventral view in situ and skeleton.

Chondrosteus acipenseroides (Agassiz 1848; Egerton 1858; Hilton and Forey 2010; Early Jurassic) is a prehistoric sturgeon without dorsal armor. It is traditionally considered a ray fin fish but nests in the LRT with ratfish and Cladoselache. Most of the skull is poorly ossified.

FIgure 2. The small sturgeon Pseudoscahirhynchus skull in several views. Note the perforated rostrum (nasal) sensitive to prey hiding in mud. The mouth is reduced to a tiny sucking tube disconnected from the quadrate. Even so, this sturgeon nests with sharks in the LRT.

FIgure 2. The small sturgeon Pseudoscahirhynchus skull in several views. Note the perforated rostrum (nasal) sensitive to prey hiding in mud. The mouth is reduced to a tiny sucking tube disconnected from the quadrate. Even so, this sturgeon nests with sharks in the LRT.

The spiral intestine question
According to this website, “The digestive system of the lamprey, posterior to the pharynx, is a simple tube. The first portion is called the esophagus, although it is not greatly different in its external appearance from the intestine which follows. Inside the intestine is found a modified fold of the intestinal lining called a typhlosole, or spiral valve. It forms a long curtain-like partition which is suspended into the lumen of the intestine through most of its length. This long typhlosole’s attachment to the intestine wall is mid dorsal at the anterior end, then spirals slightly as it progresses toward the posterior end.”

“In sharks, other chondrichthians, polypterids, sarcopterygians, sturgeons, paddlefish, bowfins, and gars, the intestine retains the spiral partition. Its spiral is more pronounced in these fish than in the lamprey.”

“Higher teleost fish loose the spiral valve modification of the intestine in favor of a lengthened system which coils about within the body cavity.”

“Intestines, urinary ducts, and reproductive passages terminate at a common space known as a cloaca in most fishes and tetrapods. Exceptions include lampreys, holocephalans, coelacanths, and therian mammals.”

Phylogenetically
I cannot make any more sense of this than what was just presented. Evidently the spiral valve comes and goes. Sturgeons, in this case, do not have a spiral valve because holocephalans (ratfish) do not have a spiral valve.

Figure x. Subset of the LRT focusing on fish and other basal vertebrates.

Figure x. Subset of the LRT focusing on fish and other basal vertebrates.


References
Agassiz L 1848. Nomenclatoris zoologici index universalis: continens nomina systematica classium, ordinum, familiarum et generum animalium omnium, tam viventium quam fossilium, secundum ordinem alphabeticum unicum disposita, adjectis homonymiis plantarum, nec non variis adnotationibus et emendationibus.
Egerton PdMG 1858. On Chondrosteus, an Extinct Genus of the Sturionidaek, Found in the Lias Formation at Lyme Regis. Philosophial Transactions of The Royal Society of London 148:871–885.
Hilton EJ and Forey PL 2010. Redescription of Chondrosteus acipenseroides Egerton, 1858 (Acipenseriformes, †Chondrosteidae) from the lower Lias of Lyme Regis (Dorset, England), with comments on the early evolution of sturgeons and paddlefishes. Journal of Systematic Palaeontology. 7(4):427–453.

wiki/Chondrosteus

Thoracopterus: a Triassic flying fish sister to giant Cretaceous Xiphactinus

Figure 1. Thoracopterus is a Triassic flying fish unrelated to extant flying fish, but a sister to giant Xiphactinus.

Figure 1. Thoracopterus is a Triassic flying fish unrelated to extant flying fish, but a sister to giant Xiphactinus.

Convergent with today’s flying fish,
Thoracopterus magnificus (Bronn 1858; Tintori and Sassi 1992; Late Triassic; Figs. 1, 2) is a derived acanthodian spiny shark with huge pectoral ray-fins likely used for short gliding attempts from the sea surface. Here speedy Thoracopterus nests in the large reptile tree (LRT, 1498 taxa) alongside giant Xiphactinus (Fig. 3), a Cretaceous predator, and informs the identity of several skull bones, now corrected.

FIgure 2. Thoracopterus skull colorized from Tintori and Sassi 1992. Tetrapod nomenclature added.

FIgure 2. Thoracopterus skull colorized from Tintori and Sassi 1992. Tetrapod nomenclature added. Note the small lateral temporal fenestra that greatly expands in Xiphactinus.

Thoracopterus also serves as a transitional taxon
demonstrating the big-eyed skull of a spiny shark together with the multi-ray fin of tradtional ray-fin fish, like Xiphactinus, something the LRT demonstrated earlier here.

Figure 3. Cretaceous Xipactinus nests equally with Cheirolepis and the crossopterygian, Gogonasus. Note the many shared traits despite the hundreds of millions of years separating them. Tetrapod bone labels are shown here. Several palatal bones, arranged in a tall arch, are visible through the cheek. Note the lacrimal is in 4 parts.

Figure 3. Cretaceous Xipactinus nests as a sister to Thoracopterus. Here several skull bones are corrected from an earlier attempt based on data from Thoracopterus.

Apologies for earlier mistakes on Xiphactinus,
here (Fig. 3) corrected. As stated many times earlier, I know nothing about a taxon until it comes up and Xiphactinus was an early attempt, now informed by Thoracopterus. Thankfully this was never published on permanent paper. Online presentations are easier to correct. Contra the critics, I do make corrections when warranted, case in point.

You’ll note, despite the many corrections,
the nesting of Xiphactinus did not change in the LRT, demonstrating the strength of the character set and the ability of any taxon to get more or less correctly nested despite intrinsic errors. Some critics think a few or several errors blackwash an entire study. Here’s hard evidence that invalidates that claim. The biggest problem with competing cladograms continues to be taxon exclusion, a point that continues to be ignored out there. Just add one a day. That’s what I do, more or less. Pretty soon, you’ll have 1500, a number that we’ll reach later this week… on just 235 characters.

Here’s the excellent Ben Thomas video
that sparked an interest in Thoracopterus.


References
Bronn HG 1858.  Beiträge zur triassischen Fauna und Flora der bituminösen Schiefer von Raibl. Neues Jahrbuch für Mineralogie, Geologie udn Paläontologie 1:1–32.
Egerton P de MG 1860. Report of the British Association for Science for 1859.
Transactions of the Sections. 116.
Leidy J 1870. [Remarks on ichthyodorulites and on certain fossil Mammalia]. Proceedings of the Academy of Natural Sciences, Philadelphia 22:12–13.
Miller RF, Cloutier R and Turner S 2003. The oldest articulated chondrichthyan from the Early Devonian period. Nature 435:501–504.
Newman M and Davidson B 2010. Early Devonian fish from the Midland Valley of Scotland. National Palaentological Congress London.14–15.
Tintori A and Sassi D 1992. Thoracopterus Bronn (Osteichthyes: Actinopterygii): A Gliding Fish from the Upper Triassic of Europe. Journal of Vertebrate Paleontology. 12 (3): 265–283.
Woodward AS 1892. On the Lower Devonian fish-fauna of Campbellton, New Brunswick. Geol. Mag. 9, 1–6.

wiki/Acanthodii
wiki/Xiphactinus
wiki/Doliodus
wiki/Thoracopterus