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Spinosaurus News ~
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The holotype collected and described by E. Stromer (1915) was incomplete, however it remains the most complete discovered. These is the plate of the bones discovered in Egypt by Stromer:
 *This image is copyright of its original author  *This image is copyright of its original author This is a photo with skeleton reconstruction of the original bones, in Munich (Germany), sadly destroyed in the world war II:  *This image is copyright of its original author Now there aren't a complete skeleton of Spinosaurus. In this photo there is a reconstruction of skeleton proposed by Ibrahim et al. (2014), with the all known Spinosaurus bones (including the holotype) colored in red:  *This image is copyright of its original author According to Ibrahim et al. (2014): "Center-of-mass estimates for several theropods have been expressed as a percentage of femoral length measured anteriorly from the hip joint. The center of mass in a biped must be located over the middle one-third of the pes to generate a plausible mid-stance pose. In our flesh rendering of Spinosaurus, the center of body mass is positioned in front of both the hip and knee joints at a distance greater than femur length, suggesting that forelimb support was required during terrestrial locomotion. Spinosaurus appears to have been poorly adapted to bipedal terrestrial locomotion. The forward position of the center of mass within the ribcage may have enhanced balance during foot-propelled locomotion in water. These adaptations suggest that Spinosaurus was primarily a piscivore....." "The locomotor adaptations outlined above, however, mark a profound departure in form an function from early spinosaurids. Prominent among these are the reduced pelvic girdle; short hindlimb; short femur; and long, low, flat-bottomed pedal unguals, all of which can be verified in the second partial skeleton described by Stromer as “Spinosaurus B”. We note here that Spinosaurus must have been an obligate quadruped on land, the first discovered among theropod dinosaurs, given the usual horizontal sacroiliac joint and the anterior location of the estimated center of body mass." "In smaller-bodied bipedal dinosaurs, short femoral proportions indicate increased stride length and enhanced speed. In Spinosaurus this is clearly not the case, given the short hindlimb. The femur in Spinosaurus has an unusually robust attachment for the caudofemoral musculature, which is anchored along nearly one-third of the femoral shaft, suggesting powerful posterior flexion of the hindlimb. The articulation at the knee joint for vertical limb support, in contrast, is reduced. The distal condyles of the femur are narrow, and the cnemial crest of the tibia is only moderately expanded. Together these features recall the shortened condition of the femur in early cetaceans and in extant semiaquatic mammals that use their hindlimbs in foot-propelled paddling." PS: I saw the anterior portion of skull exposed at the Natural History Museum in Milan, and it's really impressive, look like an enormous Mecistops sp./Crocodylus sp. Really exciting!   
I wonder if it moved similarly to a cross between a hippo and crocodile while in water?
What are the popular hypothesis' in regards to the fin's purpose?
@Pckts
According to Ibrahim et al. (2014): "Reduction of the pelvic girdle and hindlimb and the concomitant enhancement of axial-powered locomotion are common among semiaquatic vertebrates. The flexibility of the tail and the form of the neural spines in Spinosaurus suggest tail-assisted swimming. Like extinct and extant semiaquatic reptiles, Spinosaurus used lateral undulation of the tail, in contrast to the vertical axial undulation adopted repeatedly by semiaquatic mammals. The dorsal “sail” in Spinosaurus, the tallest axial structure documented among dinosaurs, has been argued to be a thermoregulatory surface, a muscle- or fat-lined hump , or a display structure. Stromer drew an analogy to the skin-covered neural spines of the crested chameleon, Trioceros cristatus (Fig. 4E). As in T. cristatus, the sail of Spinosaurus is centered over the trunk. The shape and positioning of the spine are also similar, and the base of the neural spine is expanded anteroposteriorly, with edges marked by ligament scars. In Trioceros, a tendon of multisegmental axial musculature attaches to the expanded base of the neural spine (Fig. 4E). The upper portion of the spine has sharp anterior and posterior edges, is marked by fine vertical striae, and is spaced away from adjacent spines, unlike the broader, contiguous, paddle-shaped dorsal spines of other spinosaurids. The striated surface, sharp edges, and dense, poorly vascularized internal bone of the spines suggest that they were wrapped snugly in skin and functioned as a display structure that would have remained visible while swimming."  *This image is copyright of its original author Fig.4 (E): Dorsal vertebrae with tall neural spines and spinal tendons in a cleared and stained specimen of Trioceros (Chamaeleo) cristatus (FMNH 19886). Abbreviations: ns, neural spine; sc, scapula; te, tendon of multisegment spinal muscle. Photo credits: Ibrahim et al. (2014) 
So Spino's sail wasn't used for thermoregulation, but as a display against other potential rival males? The more we know!
Another implicit question about these descriptions of the Spinosaurus: How were the relationships between spinosaurus and big crocodiles like sarcosuchus ? If the spinosaurus was quadrupedial on land, the coexistence between them would have been hard. Spinosaurus quadrupedial is supposed to be less fast, less "movable" than bipedial... And, on the other hand, despite being an aktive swimmer, under the water among these formidable opponents... I don't know.
Rather to imagine interactions with big theropods, spinosaurus had certainly to share his environment with various species of crocodiles. And I have some difficulties to imagine him as a top predator. Unless the crocs with which he coexisted were not so great and huge. I believe there are always numerous unknown facts ! (07-11-2016, 04:57 AM)Polar Wrote: So Spino's sail wasn't used for thermoregulation, but as a display against other potential rival males? The more we know! Thermoregulation is one of the many hypothesis about the function of the sail, but there isn't a real evidence that contained abundant blood vessels, that it's many vascularized, as he said Ibrahim et al. (2014) in their work. They have compared with the sail of Trioceros cristatus, saying: "The striated surface, sharp edges, and dense, poorly vascularized internal bone of the spines suggest that they were wrapped snugly in skin and functioned as a display structure that would have remained visible while swimming." (07-11-2016, 09:26 AM)Spalea Wrote: Another implicit question about these descriptions of the Spinosaurus: How were the relationships between spinosaurus and big crocodiles like sarcosuchus ? If the spinosaurus was quadrupedial on land, the coexistence between them would have been hard. Spinosaurus quadrupedial is supposed to be less fast, less "movable" than bipedial... And, on the other hand, despite being an aktive swimmer, under the water among these formidable opponents... I don't know. It's an interesting question, but i think there isn't a complete answer because we can't know exactly which relationship they could have, but we can only guess. Surely it must have been a sight see a meeting between these two giants. Actually, Spinosaurus is a quadruped obligate according to Ibrahim et al. (2014), but there are no current evidence now that demonstrate quadrupeds in Theropoda suborder. All theropods is bipeds obligate, because they couldn't pronate their hands. The quadruped Spinosaurus it's calculated with a virtual reconstruction based on the center of mass estimate, but not to a fossil data. Spinosaurus ambulate in quadrupedal posture leaning alternately forelegs, particularly with the support of the knuckles. This hypothesis is to the detriment of the Spinosaurus quadruped, especially for a theropods like a spinosaurus with the estimated weight of 6-8 tons. I think that as long as you don't find a complete skeleton, you will not know for sure many question marks. I hope i have writed clearly. 
Dear god, I hope for the love of god Spino is not quad but a bipedal like in Jurassic Park....
@genao87, the investigation is still up in the air, leaning toward a quadruped, semiaquatic creature. Nonetheless, here is the critique of the Ibrahim et al. (2014) paper. The author's main point is correcting the scaling results in this body type:
 *This image is copyright of its original author Also, Ibrahim et al. (2014) may have incorrectly meshed two different species into one skeleton according to this paper. The same paper says Spinosaurus B (our semiaquatic quadruped from Ibrahim et al. (2014)) was not the same as Stromer's (1915) famous Spinosaurus specimen due to morphological differences in the long bones. I'm not advocating either stance as I have no where near enough knowledge on the subject. (08-23-2016, 12:03 AM)tigerluver Wrote: @genao87, the investigation is still up in the air, leaning toward a quadruped, semiaquatic creature. Nonetheless, here is the critique of the Ibrahim et al. (2014) paper. The author's main point is correcting the scaling results in this body type: Now this is refreshing news...I hope this gives rise to the old Spino. Good to know that a different specimen was used and it is still up in the air.
More on Spinosaurus
Here are some big points the author proposed:
Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa Hendrickx, Mateus & Buffetaut, 2016
 *This image is copyright of its original author Fig 11. Comparison of the snout of two specimens of Spinosaurus from the ‘Continental intercalaire’ of Northwestern Africa. A–H, Fused maxillae and premaxillae of A–B, E, G, MSNM V4047 referred to Spinosaurus aegyptiacus by Dal Sasso et al. [21] (courtesy of Simone Maganuco); and C–D, F, H, MNHM SAM 124 referred to Spinosaurus maroccanus (nomen dubium) by Taquet and Russell [93] in A, C, lateral; B, D, anterior; E, F, ventral; and G, H, dorsal views. Abbreviation: mx9, ninth maxillary alveolus; pmx6, sixth premaxillary alveolus, pmx7, seventh premaxillary alveolus. Scale = 20 cm (A, E, G), 10 cm (C, F, H), 5 cm (B), 2 cm (D).  *This image is copyright of its original author Fig 15. Jaw mechanics in the spinosaurid Spinosaurus. A–D, Mandibular articulation; and F, G, skull in A, C, F–G, lateral; and B, D, anterior views; when A–B, F, the mouth is closed; and C–D, G, fully open, illustrating the lateral movement (in red) of the mandibular ramus for a 45° rotation of the lower jaw (courtesy of Jaime A. Headden); E, skeletal reconstruction of Spinosaurus aegyptiacus by Ibrahim et al. [22]) in swimming position in lateral view with a human (1.8 m) as a scale (modified from Ibrahim et al. [22]). This model is based on spinosaurid cranial and postcranial remains (colored in red) from the Albian-Cenomanian of Northern Africa which possibly belong to two spinosaurine taxa (see also Evers et al. [27]); H, reconstruction of a semi-aquatic Spinosaurus in fishing position (i.e., jaws wide open) in anterolateral view (courtesy of Jason Poole). Abbreviations: an, angular; ar, articular; d, dentary; ecc, ectocondyle; enc, entocondyle; j, jugal; m, maxilla; n, nasal; p, parietal; pm, premaxilla; po, postorbital; pt, pterygoid; ptf, pterygoid flange; q, quadrate; qf, quadrate foramen; qj, quadratojugal; retp, retroarticular process of the articular; sa, surangular; sq, squamosal. Abstract: "Six quadrate bones, of which two almost certainly come from the Kem Kem beds (Cenomanian, Upper Cretaceous) of south-eastern Morocco, are determined to be from juvenile and adult individuals of Spinosaurinae based on phylogenetic, geometric morphometric, and phylogenetic morphometric analyses. Their morphology indicates two morphotypes evidencing the presence of two spinosaurine taxa ascribed to Spinosaurus aegyptiacus and? Sigilmassasaurus brevicollis in the Cenomanian of North Africa, casting doubt on the accuracy of some recent skeletal reconstructions which may be based on elements from several distinct species. Morphofunctional analysis of the mandibular articulation of the quadrate has shown that the jaw mechanics was peculiar in Spinosauridae. In mature spinosaurids, the posterior parts of the two mandibular rami displaced laterally when the jaw was depressed due to a lateromedially oriented intercondylar sulcus of the quadrate. Such lateral movement of the mandibular ramus was possible due to a movable mandibular symphysis in spinosaurids, allowing the pharynx to be widened. Similar jaw mechanics also occur in some pterosaurs and living pelecanids which are both adapted to capture and swallow large prey items. Spinosauridae, which were engaged, at least partially, in a piscivorous lifestyle, were able to consume large fish and may have occasionally fed on other prey such as pterosaurs and juvenile dinosaurs." |
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