Art: Dilophosaurus wetherilli

Tussling theropods has been a classic depiction of paleoart ever since Charles R. Knight painted a beautiful canvas of two Dryptosaurus. Since then, Dilophosaurus has often been featured and I know I am not the first to illustrate something of this nature. Of course, the coloration is purely speculative but I thought that, with crests like they have, they must have made a fantastic display.

Art: Archaeopteryx lithographica

I actually made three previous drawings of this bird but they were all unsatisfying in some respect. The first looked to dinosaurian, the second was posturing strangely. This one seemed to be the best. Although not particularly well preserved in Archaeopteryx, I felt the long leg feathers were appropriate since most other flying deinonychosaurs had them. In spite of its very birdlike appearance, I prefer to consider Archaeopteryx a dinosaur because its basic anatomy is nearly identical to that of the dromaeosaurids and other Deinonychosauria that are nearly always considered dinosaurs. Archaeopteryx might even belong to the same created kind as Velociraptor, implying that it too had feathers.

Achillobator giganticus

Perle, Norell, et Clark 1999

Evidence: partial skull and fragmentary skeleton

Cenomanian to Santonian

Bayanshiree Svita

Dornogov’; Mongolia

Biology: 5 meters long – 250 kilograms

Since it is known from only a single specimen, not much is known of Achillobator biology. It is believed that, given its comparably large size, it preyed on much larger dinosaurs than other dromaeosaurids might (Paul 2010). However, the most common herbivores of the Bayanshiree were ankylosaurs and therizinosaurs. Hadrosaurs were rare, with only one known species, Bactrosaurus mongoliensis. While it seems very likely that Achillobator might have preferred a hadrosaur to a potentially dangerous therizinosaur or ankylosaur but, given the frequencies of the later herbivores, it probably evolved its large size to cope with the more formidable herbivores. It probably wasn’t fast enough to take down the ornithomimid Garudimimus brevipes also found in the Bayanshiree. Achillobator may have competed with Alectrosaurus but, because of the dubious nature of that tyrannosaur, how they might have competed would be speculation at best. Perhaps the tyrannosaur pursued primarily hadrosaurs, limiting conflicts.

Evolution

There is very little controversy over the placement of Achillobator in the Dromaeosauridae and, more specifically, in the Dromaeosaurinae. It appears to be closest to Utahraptor and Dromaeosaurus (Senter et al. 2012).

References:

Paul, G. S. 2010. The Princeton Field Guide to Dinosaurs. Princeton, NJ: Princeton University Press.

Senter, P., J. I. Kirkland, D. D. DeBlieux, S. Madsen, et N. Toth. 2012. “New Dromaeosaurids (Dinosauria: Theropoda) from the Lower Cretaceous of Utah, and the Evolution of the Dromaeosaurid Tail.” PLoS ONE 7(5): e36790.

Aachenosaurus multidens

Smets 1888

Invalid: Plantae indet.

Dürrestein Formation

Carnian

Regione Veneto, Italy

Dinosaurs:

Prosauropoda indet.

Other Animals:

            Margarosmilia sp.

            Cryptocoelia zitteli

            Amblysiphonella sp.

            Atrochaetetes medius

            Jablonskyia andrusovi

            Uvanella irregularis

Plants:

Solenopora sp.

            Dendronella sp.

Notes:

This appears to be a marine deposit, dominated by brain corals, sponges, and kelp (Tosti et al. 2014). However, Weishampel et al. (2007) reported possible prosauropod tracks for the formation. Perhaps this lone dinosaur wandered over the drying reef as the water receded into the giant wave that would contribute to the preservation of the unwary ecosystem.

References:

Tosti, F., A. Mastandrea, A. Guido, F. Demasi, F. Russo, et R. Riding. 2014. “Biochemical and redox record of mid-late Triassic reef evolution in the Italian Dolomites.” Paleogeography, Paleoclimatology, Paleoecology 399: 52-66.

Weishampel, D. B., P. M. Barrett, R. A. Coria, J. L. Loeuff, X. Xing, Z. Xijin, A. Sahni, E. M. P. Gomani, C. R. Noto. 2007. “Dinosaur Distribution.” In D. B. Weishampel, P. Dodson, and H. Osmólska. The Dinosauria, Second Edition. Berkeley, CA: University of California Press. 517-606.

Isalo II Formation (Makay Formation)

Anisian to Carnian

Faritany Toliara, Madagascar

Dinosaurs:

Theropoda indet.

Prosauropoda indet.

Sauropoda indet.

Other Animals:

Asteracanthus sp.

Osteichthyes indet.

Colobodontidae indet.

Semionotidae indet.

Stegocephali indet.

Metoposauridae

Metoposaurus hoffmani

Procolophonidae indet.

Reptilia indet.

Phytosauria indet.

Phytosauridae indet.

Rhynchosauria indet.

Unnamed rhynchosaur species

Isalorhynchus genovefae (including Hyperodapedon genovefae)

Azendohsaurus madagaskarensis

Archosauria indet.

Pseudosuchia indet.

Sphenodontia indet.

Synapsida indet.

Kannemeyeriiformes indet.

Chiniquodon kalanoro

Unnamed traversodontid species

Unnamed traversodontid species

Dadadon isaloi

Menadon besairiei

Notes:

Usually considered an ancient streambed, the Isalo Group likely represents a flooding event or series of events that overtook the valley during early Triassic colonization of the region. Although it contains what appears to be the tooth of a sauropod (Burmeister et al. 2006), Weishampel et al. (2007) listed only prosauropods for the formation and may have been indicating that the tooth, and possibly other teeth assigned to Theropoda, might be prosauropods, or that the confusing archosauromorph genus Azendohsaurus is a dinosaur. In all honesty, it is a little presumptive to assume these teeth belong to anything specifically. All the misidentification has contributed to confusion over the assigned epoch of the strata, but other genera certainly nail down a Triassic or possibly very early Jurassic date. Freshwater hybodontiform sharks were common along with giant salamander-like metoposaurs. On the land, dinosaurs were rare and, as of yet, no specific families have been identified. A few species of cynodonts, from herbivorous traversodonts to hunting Chiniquodon, were relatively common. It seems the bulky dicynodonts were even more rare than dinosaurs. The crazy Azendohsaurus seems to have had a little head, a long neck, and stump legs. As these weirdoes attest, bizarre reptiles dominated fauna. Crocodile-like phytosaurs made watering holes dangerous places and the pseudosuchians, crocs of the land, made terrestrial life equally uncomfortable.

References:

Burmeister, K. C., J. J. Flynn, J. M. Parrish, et A. R. Wyss. 2006. “Paleogeographic and biostratigraphic implications of new early Mesozoic vertebrates from Poamay, central Morondava Basin, Madagascar.” In J. D. Harris, S. G. Lucas, J. A. Spielmann, M. G. Lockley, A. R. C. Milner, et J. I. Kirkland. The Terrestrial Triassic-Jurassic Transition. New Mexico Museum of Natural History and Science Bulletin 37: 457-475.

Weishampel, D. B., P. M. Barrett, R. A. Coria, J. L. Loeuff, X. Xing, Z. Xijin, A. Sahni, E. M. P. Gomani, C. R. Noto. 2007. “Dinosaur Distribution.” In D. B. Weishampel, P. Dodson, and H. Osmólska. The Dinosauria, Second Edition. Berkeley, CA: University of California Press. 517-606.

La Colonia Formation

Campanian to Maastrichtian

Provincia de Chabut, Argentina

Dinosaurs:

Theropoda indet.

Carnotaurus sastrei

            Titanosauria indet.

Ankylosauria indet.

Hadrosauroidea indet.

Other Animals:

            Elasmosauridae indet.

            Sulcusuchus erraini

            Meiolaniidae indet.

            Patagoniaemys gasparinae

            Chelidae indet.

Yaminuechelys gasparinii

Serpentes indet.

Madtsoiidae indet.

Alamitophis argentines

Boidae indet.

Enantiornithes indet.

Argentodites coloniensis

Coloniatherium cilinskii

Reigitherium bunodontum

Plants:

Azolla sp.

Crybelosporites pannuceus

Cyathidites australis

Dicksonia sp.

Gleicheniidites senonicus

Lugiomarsiglia aquatica

Mirasolita irupensis

Molaspora lobata

Paleoazolla patagonica

Regnellidium thomas-taylorii

Classopollis sp. 1

Classopollis sp. 2

Cheirolepidiaceae indet.

Lygistepollenites sp.

Microchacrydites sp.

Podocarpidites spp.

Arecipites spp.

Dicotyledoneae indet.

Inaperturotetradites sp.

Intratriporopollenites sp.

Araceae indet.

Arecaceae indet.

Nelumbo puertae

Pandaniidites sp.

Peninsulapollis sp.

Nelumbonaceae indet.

Sparganiaceaepollenites sp.

Typha sp.

Typhaceae indet.

Botryococcus sp.

Botryococcus braunii

Pediastrum sp. 1

Pediastrum sp. 2

Pediastrum boryanum

Mougeotia sp.

Spirogira sp. 1

Spirogira sp. 2

Zygnema sp.

Fungi indet.

Notes:

Despite the 1980s discovery of the horned theropod Carnotaurus in the formation, nothing has been published on other dinosaur remains from the formation. However, some fantastic research has detailed the plant life of the formation, providing a fairly accurate picture of the environment. It was a swamp, possibly near the mouth of a river, emptying into a larger body of water. It is a good possibility that it was part of a seacoast at the time, before flooding or a landslide of some kind apparently buried both terrestrial and aquatic inhabitants. Besides dinosaurs on land, snakes, particularly boids and their relatives, like Alamitophis, were common. They preyed on a variety of small mammals, including multituberculates and dryolestids. The most common were Coloniatherium, a rat-like dryolestid. The water was full of turtles, including relatives of the modern mata mata and the amazingly horny meiolaniid Patagoniaemys. Commonly plying through the deeper water were elasmosaurs, classic, long-necked plesiosaurs. Sulcusuchus was also a large mobile plesiosaur, but of a short-necked, long-snouted kind. The plant life of the La Colonia is a fascinating subject. Cúneo et al. (2014) is a great read and details the genera and kinds of plants that dominated, from open water to shoreline into the forest. It seems that floating plants like Azolla and water lettuce were dense in calm water while lotus and aquatic ferns grew in shallow water and cattails lined the shore. Tree ferns and palms dominated the forest.

References:

Cúneo, N. R., M. A. Gandolfo, M. C. Zamaloa, et E. Hermsen. 2014. “Late Cretaceous aquatic plant world in Patagonia, Argentina.” PLoS ONE 9(8): e104749