[Paleontology • 2023] A Reappraisal of the Cranial and Mandibular Osteology of the spinosaurid Irritator challengeri (Dinosauria: Theropoda)

Irritator challengeri  Martill, Cruickshank, Frey, Small & Clarke, 1996

in Schade, Rauhut, Foth, Moleman et Evers, 2023. 

DOI: 10.26879/1242

 twitter.com/LordTrilobite

ABSTRACT

Although originally described almost three decades ago, the holotype of Irritator challengeri from the Lower Cretaceous Romualdo Formation of Brazil still represents the most complete spinosaurid skull known to science. Here, we present a detailed description of the skull of Irritator based on digital reconstructions from medical and micro computed tomography (µCT) data. Segmentation reveals the near-complete palatal complex and braincase, an unusual morphology of the retroarticular process, a large, ventrally inclined surangular shelf and the tooth replacement pattern. The digitally reconstructed skull anatomy indicates a robust dentition, a field of binocular vision in front of the skull with an inclined snout orientation, a relatively weak but fast bite, as well as laterally spreading and rotating lower jaw rami during jaw opening. We modified an existing phylogenetic matrix of Tetanurae to account for new observations on the morphology of Irritator and analysed this using parsimony and Bayesian methods. Results support Spinosauridae as members of Megalosauroidea and recover a monophyletic Carnosauria (Megalosauroidea + Allosauroidea). Parsimony analysis recovers Monolophosaurus nested within Megalosauroidea as sister taxon to spinosaurids, but this is not supported by the Bayesian analysis. Bayesian time-calibration and evolutionary rate analysis indicate that spinosaurid evolution happened fast, despite a long ghost lineage of at least 35 million years. High evolutionary rates over a prolonged time can explain the highly derived skull morphology of spinosaurids. This study provides an in-depth look into the evolution of spinosaurid skull anatomy and refines our understanding of these specialized Mesozoic predators.

Keywords: Dinosaur; Theropod; Spinosaurid; Cretaceous; Mesozoic; Brazil

Theropoda Marsh, 1881

Tetanurae Gauthier, 1986

Megalosauroidea Fitzinger, 1843; sensu Carrano et al. (2012)

Spinosauridae Stromer, 1915

Spinosaurinae (Stromer, 1915); sensu Sereno et al. (1998)

Irritator challengeri Martill, Cruickshank, Frey, Small and Clarke, 1996

Holotype. SMNS 58022, largely complete skull, missing most of the premaxillae, anterior ends of the maxillae, and anteriormost parts of both mandibles.

Locality and horizon. Near Buxexé, close to Santana do Cariri, Ceará State, northeastern Brazil (see Sues et al., 2002: 535). Lower part of the Romualdo Formation (Santana Formation of some authors; see discussion in Arai and Assine, 2020) of the Santana Group, late Aptian (Arai and Assine, 2020).

Marco Schade, Oliver W. M. Rauhut, Christian Foth, Olof Moleman, and Serjoscha W. Evers. 2023. A Reappraisal of the Cranial and Mandibular Osteology of the spinosaurid Irritator challengeri (Dinosauria: Theropoda). Palaeontologia Electronica. 26(2): a17.DOI: 10.26879/1242

 

palaeo-electronica.org/content/2023/3821-the-osteology-of-irritator

 twitter.com/LordTrilobite/status/1656583542720086016

[Paleontology • 2021] Cranial Anatomy of Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996 (Reptilia: Ichthyosauria) from the Middle Triassic Besano Formation of Monte San Giorgio, Italy/Switzerland: Taxonomic and Palaeobiological Implications

Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996

in Bindellini​, Wolniewicz, ... et Dal Sasso​, 2021. 

DOI: 10.7717/peerj.11179 

facebook.com/AndrzejWolniewicz14 

Abstract 

Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996 was described on the basis of a single fossil excavated near Besano (Italy) nearly three decades ago. Here, we re-examine its cranial osteology and assign five additional specimens to B. leptorhynchus, four of which were so far undescribed. All of the referred specimens were collected from the Middle Triassic outcrops of the Monte San Giorgio area (Italy/Switzerland) and are housed in various museum collections in Europe. The revised diagnosis of the taxon includes the following combination of cranial characters: extreme longirostry; an elongate frontal not participating in the supratemporal fenestra; a prominent ‘triangular process’ of the quadrate; a caudoventral exposure of the postorbital on the skull roof; a prominent coronoid (preglenoid) process of the surangular; tiny conical teeth with coarsely-striated crown surfaces and deeply-grooved roots; mesial maxillary teeth set in sockets; distal maxillary teeth set in a short groove. All these characters are shared with the holotype of Mikadocephalus gracilirostris Maisch & Matzke, 1997, which we consider as a junior synonym of B. leptorhynchus. An updated phylogenetic analysis, which includes revised scores for B. leptorhynchus and several other shastasaurids, recovers B. leptorhynchus as a basal merriamosaurian, but it is unclear if Shastasauridae form a clade, or represent a paraphyletic group. The inferred body length of the examined specimens ranges from 1 m to about 8 m. The extreme longirostry suggests that B. leptorhynchus primarily fed on small and elusive prey, feeding lower in the food web than an apex predator: a novel ecological specialisation never reported before the Anisian in a large diapsid. This specialization might have triggered an increase of body size and helped to maintain low competition among the diverse ichthyosaur fauna of the Besano Formation.

Figure 3: The most complete skeletons of Besanosaurus leptorhynchus.  
 (A) PIMUZ T 1895; (B) BES SC 999; (C) PIMUZ T 4376 (with a Mixosaurus specimen above it); (D) PIMUZ T 4847.

Scale bars represent 50 cm.

Figure 4: Skull and mandible of Besanosaurus leptorhynchus holotype BES SC 999, and interpretative drawings.
 Grey dashed lines and grey labels indicate elements not visible on the surface, grey areas indicate background sediment, light grey areas indicate background bone.

 Scale bar represents 10 cm.

Figure 20: Cranial reconstruction of Besanosaurus leptorhynchus.
Articulated skull and mandible in (A) left rostrolateral, (B) caudal (occipital), (C) dorsal, (D) left lateral, and (E) ventral (palatal) view.

 Line drawings by Marco Auditore.

 Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996

Conclusions: 

In general, the specimens here described preserve and represent a remarkably complete cranial anatomy, so that Besanosaurus leptorhynchus now is among the best-understood Middle Triassic Ichthyosaur taxa to date. Our revision of the skull morphology of this taxon clarified long-standing controversies regarding its cranial anatomy and the taxonomy of shastasaurids from Monte San Giorgio. Based on this rich fossil material, we have demonstrated that Mikadocephalus gracilirostris (GPIT 1793/1) is a junior synonym of Besanosaurus leptorhynchus, providing evidence to refute previous hypotheses (Maisch & Matzke, 1997a, 2000; Maisch, 2010) about the co-occurrence of two different shastasaurid taxa (Besanosaurus and Mikadocephalus) in the Besano Formation.

The six specimens here described represent a potential ontogenetic series covering a certain size range of mainly adult and potentially subadult specimens (Fig. 19), ordered by increasing size as follows: PIMUZ T 4376, PIMUZ T 1895, BES SC 999, BES SC 1016, GPIT 1793/1, PIMUZ T 4847. An allometric growth signal, yet to be fully tested, has also been detected. Other sources of intraspecific variation such as sexual dimorphism, cannot be ruled out, however, partly due to the limited dataset. Here we also report evidence that Besanosaurus was the largest Middle Triassic ichthyosaur taxon of the Western Tethys since we confidently estimate a fully adult size of about 8 m for specimen PIMUZ T 4847.

Besanosaurus possesses an extremely long, slender, and gracile snout, representing an ecological specialization never seen before the Anisian in a large sized (~8 m) diapsid. The diagnostic, prominent coronoid (preglenoid) process of the surangular and a large rugose area for the attachment of the mAMES allow to infer the presence of well-developed jaw closing muscles, which likely had an important functional role: we assume an efficient and fast jaw closing movement and hypothesize a snap-feeder-like hunting strategy, with a specific preference for small and elusive prey (such as coleoids and/or small fishes). Among the ichthyosaurian Besano-Monte San Giorgio Fauna (Cymbopondylus, mixosaurids, and Besanosaurus), different hunting strategies, demonstrated by different morphologies and dimensions of the rostra, should have led to the maintenance of low interspecific competition (i.e., niche partitioning). We also hypothesize that the specialization represented by a longirostrine morphology might have been driven by prey preference and the methods of prey capture. Mixosaurus and Cymbospondylus show almost a global distribution; on the contrary, Besanosaurus is known only from the Besano Formation (Italy and Switzerland). A wider distribution of this genus is expected (and supported by McGowan & Motani, 2003: 135–136): it seems unlikely to us that Besanosaurus would be represented only in the Alpine Tethys realm.

Last but not least, the importance of Besanosaurus is not only given by the completeness and remarkable preservation of its remains, and its ecological role, but also by the key phylogenetic position occupied by the taxon in the ichthyosaurian phylogeny: our analysis, performed with a matrix that includes around 90% of unambiguous scores for B. leptorhynchus and revised scores for other Triassic taxa, shows that this taxon represents the basalmost member of shastasaur-grade ichthyosaurs.

Gabriele Bindellini​, Andrzej S. Wolniewicz, Feiko Miedema, Torsten M. Scheyer and Cristiano Dal Sasso​. 2021. Cranial Anatomy of Besanosaurus leptorhynchus Dal Sasso & Pinna, 1996 (Reptilia: Ichthyosauria) from the Middle Triassic Besano Formation of Monte San Giorgio, Italy/Switzerland: Taxonomic and Palaeobiological Implications. PeerJ. 9:e11179. DOI: 10.7717/peerj.11179

 facebook.com/AndrzejWolniewicz14/posts/4165706186814712

 

[Botany • 2020] Cyanea kuhihewa: Rediscovering One of Hawai'i's Rarest Trees

Cyanea kuhihewa Lammers

in Rønsted & Wood, 2020. 

 DOI: 10.1002/ppp3.10099 

 twitter.com/PlantsPplPlanet

Abstract

Cyanea kuhihewa is a Hawaiian plant thought to be extinct but recently rediscovered. Oceanic island plants are uniquely adapted to their environment. Globally, many island species are now threatened needing extensive conservation management to survive. We highlight this global conservation challenge and provide an example from Hawai'i of how we may safeguard critically endangered species from extinction.

  Cyanea kuhihewa Lammers. 

(a) Habitat North shore Kaua'i. (b) Map of Kaua'i showing Limahuli Valley. (c–e) Habit and flowers.

 Photographs and map (a,b) by Ken Wood; (c‐e) by David Lorence

CONCLUDING REMARKS: 

The flora of Hawai'i is a hotspot of endemism, but the uniquely adapted native flora is highly vulnerable to disturbance, and losing just a few populations may mean losing one or more species. C. kuhihewa is one of about 85 taxa in this genus of charismatic Hawaiian lobeliads, most of which are uniquely adapted to a single island or are even narrower endemics from a single mountain or valley. About half of the genus is considered threatened, most of them with fewer than 50 individuals remaining in the wild. Reports of rediscovery of species previously thought to be extinct are always encouraging news, and we may still be able to safeguard C. kuhihewa through the ongoing combination of monitoring, weed and predator control, seed‐banking, propagation, and out‐planting.

Nina Rønsted and Kenneth R. Wood. 2020. Cyanea kuhihewa: Rediscovering One of Hawai'i's Rarest Trees. PLANTS, PEOPLE, PLANET. DOI: 10.1002/ppp3.10099

 twitter.com/PlantsPplPlanet/status/1229716541815521280  #FloraObscura  

   

[Mammalogy • 1996] Caenolestes condorensis • A New Species of northern Shrew Opossum (Paucituberculata: Caenolestidae) from the Cordillera del Condor, Ecuador

 Caenolestes condorensis

Andean caenolestid or Andean Shrew Opossum

: a species of shrew opossum (family Caenolestidae). 

It is known from one location at an altitude of 2000 m in the Cordillera del Cóndor in Ecuador.

Albuja, V. L. and Patterson, B. D. 1996. A New Species of northern Shrew Opossum (Paucituberculata: Caenolestidae) from the Cordillera del Condor, Ecuador. Journal of Mammalogy. 77(1): 41-53.

http://bibdigital.epn.edu.ec/bitstream/15000/4750/1/Caenolestes-Cordillera%20del%20Cóndor1996.pdf

https://sites.google.com/a/fieldmuseum.org/bruce-pattersons-lab/Home/publications/prior-publications

http://www.nysm.nysed.gov/mammalsrevealed/species/shrew.html

[Herpetology • 1996] Batrachoseps gabrieli • A new species of Batrachoseps (Amphibia: Plethodontidae) from the San Gabriel Mountains, southern California

Batrachoseps gabrieli 

San Gabriel Mountains Slender Salamander

photo: http://www.californiaherps.com/salamanders/pages/b.gabrieli.html

 

Wake, D.B. 1996. A new species of Batrachoseps (Amphibia: Plethodontidae) from the San Gabriel Mountains, southern California. Natural History Museum of Los Angeles County - Contributions in Science: 1-12.  http://www.nhm.org/site/sites/default/files/pdf/contrib_science/CS463.pdf

http://www.californiaherps.com/salamanders/pages/b.gabrieli.html

[Paleontology • 2006] Dakosaurus andiniensis | An Unusual Marine Crocodyliform from the Jurassic-Cretaceous Boundary of Patagonia

Remains of the marine crocodyliform Dakosaurus andiniensis from western South America reveal a lineage that drastically deviated from the skull morphology that characterizes marine crocodyliforms. The snout and lower jaw are extremely robust, short, and high and only bear a few large teeth with serrated edges (resembling those of some terrestrial carnivorous archosaurs). This unusual morphology contrasts with the long and gracile snout and lower jaws bearing numerous teeth, which are present in the closest relatives of D. andiniensis (and interpreted as indicating feeding on small fish or mollusks). Thus, the morphological diversity of pelagic marine crocodyliforms was wider than had been thought.

Gasparini Z., et al. 2006. An Unusual Marine Crocodyliform from the Jurassic-Cretaceous Boundary of Patagonia. Science. 70-73. DOI: 10.1126/science.1120803

http://patagoniamonsters.blogspot.com/2010/05/lake-monsters-are-dakosaurs-not.html

[Paleontology • 1959] Arambourgiania philadelphiae • One of the world's largest flying animals: (Pterosauria, Pterodactyloidea)

Image copyright Joe Tucciarone

Genus: Arambourgiania Nesov et al., 1987

Species: A. philadelphiae (Arambourg, 1959) (type)

Synonym: Titanopteryx Arambourg, 1959 (preoccupied)

Arambourgiania is a pterosaur from the Late Cretaceous (Maastrichtian) of Jordan. It was one of the largest members of this group.

http://www.dinosaurfact.net/Pterosaurs/Arambourgiania.php

http://en.wikipedia.org/wiki/Arambourgiania

Arambourg, C. 1959. Titanopteryx philadelphiae nov. gen., nov. sp. Ptérosaurien géant. Notes Mém. Moyen-Orient. 7: 229–234

Frey, E. & Martill, D.M. 1996. A reappraisal of Arambourgiania (Pterosauria, Pterodactyloidea): One of the world's largest flying animals. N.Jb.Geol.Paläont.Abh. 199(2): 221-247

Martill, D.M., E. Frey, R.M. Sadaqah & H.N. Khoury. 1998. Discovery of the holotype of the giant pterosaur Titanopteryx philadelphiae Arambourg 1959, and the status of Arambourgiania and Quetzalcoatlus. Neues Jahrbuch fur Geologie und Paläontologie. Abh. 207(1): 57-76

[Paleontology • 1996] Irritator challengeri • A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil

Irritator challengeri Martill et al., 1996

Martill, D. M.; Cruickshank, A. R. I.; Frey, E.; Small, P. G.; Clarke, M. (1996). "A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil". Journal of the Geological Society 153: 5. doi:10.1144/gsjgs.153.1.0005.

[Herpetology • 1996] Brookesia exarmata • a new dwarf chameleon (Reptilia, Chamaeleonidae) from the limestone outcrops of western Madagascar

Dwarf Chameleon (Brookesia exarmata)

Amber Mountain National Park, Madagascar

http://www.superstock.com/stock-photos-images/4201-60199

Abstract

During fieldwork carried out in January-February 1995 in the Strict Nature Reserve No. 9 (western Madagascar), a new species of dwarf chameleon (genus Brookesia) was discovered on the western slopes of the Antsingy forest. The inaccessible habitat of this new taxon consists of dense subhumid tropophile forest growing among the limestone blocks belonging to the huge karstic complex of the Massif, where Brookesia exarmata sp. nov. is sympatric with Brookesia perarmata, a taxon likely endemic to the Antsingy forest, and Brookesia brygooi. The new taxon, formally described in this paper, is a small-sized chameleon whose total adult length ranges between 30 and 45 millimetres: this feature, together with the absence of a pelvic shield and the presence of a series of dorsolateral tubercles (or a few small dorsolateral spines), leads to Brookesia exarmata being ascribed to the Brookesia minima group. Brookesia tuberculata and Brookesia peyrierasi are ressurrected from the synonymy of Brookesia minima and a new identification key to these and to the other three species included in the Brookesia minima group is proposed.

Type locality: River Ambodyreana, Tsingy de Bemaraha, Antsalova, Fivondronana, Mahajanga Province, Madagascar.

Schimmenti G; Jesu R 1996. Brookesia exarmata sp. nov. (Reptilia, Chamaeleonidae): a new dwarf chameleon from the limestone outcrops of western Madagascar. ITALIAN JOURNAL OF ZOOLOGY (MODENA) 63(2) 1996: 193-197

[Herpetology • 1996] Philautus refugii • Western Lowland Bush Frog (Rhacophoridae) from Malaysia's Borneo

Philautus refugii Inger & Stuebing, 1996

Philautus refugii is a species of frog in the Rhacophoridae family. It is found in Malaysia and possibly Indonesia. Its natural habitat is subtropical or tropical moist lowland forests.

List as Vulnerable - VU by IUCNRedlist

Philautus refugii from frogsofborneo.org

Philautus refugii from arkive.org

http://amphibiaweb.org/browseimgs/photos_Philautus.html

[Herpetology • 1996] Philautus gunungensis • Montane bush frog (Rhacophoridae) from Kinabalu, Malaysia

© 2009 Maximilian Dehling:

http://calphotos.berkeley.edu/cgi/img_num=302418

Philautus gunungensis Malkmus & Riede, 1996

describe in the same paper with Philautus saueri