Guanlong and Dilong: basal allosaurs, not basal tyrannosaurs
I thought more taxa
would help the present shifting of taxa from their original designations, seen here, here and here.
Figure 1. Guanlong reconstructed by moving elements tracing Xu et al. 2006. The robust foot and small skull are notable.
Giuanlong wucaii (Xu et al. 2006, Late Jurassic, China, 3m long) was originally considered a basal tyrannosauroid. An adult (IVPP V14531) and a more complete juvenile (IVPP V14532) are known. The adult had an elaborate medial nasal head crest. The juvenile had a smaller crest restricted to the anterior.
Figure 2. Theropod cladogram. Guanlong nests with two other putative tyrannosaurs, Dilong and Yutyrannus, along with feathered Sinocalliopteryx and Allosaurus.
Here Guanlong nests
in the large reptile tree (Fig. 1) at the base of the Allosaurus clade, not the T-rex clade. But note the Allosaurus clade nests at the base of the T-rex clade. Remember I’m using generalized traits to lump and separate my taxa, not traits specific to theropods.
According to Xu et al. 2006
traits Guanlong shares with tyrannosauroids largely exclusive of other theropods include:
- large foramina on the lateral surface of the premaxilla
- tall premaxillary body
- fused nasals
- a large frontal contribution to the supratemporal fossa
- a pneumatic jugal foramen in the posterior rim of the antorbital fossa
- a deep basisphenoidal sinus with large foramina
- a subcondylar recess on the basisphenoid
- the supraoccipital excluded from the foramen magnum
- the short retroarticular process
- the relatively small, U-shaped premaxillary teeth that are arranged in a row more transversely than anteroposteriorly oriented
- and labio-lingually thick maxillary and dentary teeth
- Striking tyrannosauroid pelvic features include an ilium subequal to femoral length, a distinctive dorsal concavity on the pre-acetabular process, a supracetabular crest that is straight in dorsal view, a prominent median vertical crest on the lateral surface of the ilium, a concave anterior margin of the pubic peduncle, a pubic tubercle close to the dorsal part of the pubic shaft, an extremely large pubic boot (55% of pubic length), and a thin sheet of bone extending from the obturator process down the ischial shaft
None of these are character traits listed in the large reptile tree. The authors note, “Guanlong represents a specialized lineage in the early evolution of tyrannosauroids.”
Figure 3. The CM 31374 specimen of Coelophysis. The long snout becomes progressively shortened in the Guanlong/Dilong clade.
The unusually long snout of Guanlong
might appears to be elongated in order to support a larger crest. The authors note, “Cranial horns, bosses and crests are present in many non-avian theropods and are best exemplified by Dilophosaurus, Monolophosaurus and oviraptorids, among others.” However, Guanlong is also derived from a sister to Coelophysis, which also had a longer rostrum and similar proportions.
Figure 4. Dilong paradoxus. Images from Xu et al. 2004. Colors added.
Dilong paradoxus (Xu et al., 2004 TNP01109) Early Cretaceous ~125 mya, 2.75 m in length, was also originally considered a basal tyrannosauroid. In the large reptile tree (Fig. 2) it is derived from a sister to Guanlong at the base of the Allosaurus/Sinocalliopteryx clade. Dilong was larger than Guanlong and covered with feathers or protofeathers. Here the snout is shorter still.
None of these taxa
are known to have stiff wing feathers as seen in the tyrannosaurs, like Zhenyuanlong, and later clades leading to birds.
References
Xu X, Clark JM, Forster CA, Norell MA, Erickson GM, Eberth DA, Jia C and Zhao Q 2006. A basal tyrannosauroid dinosaur from the Late Jurassic of China” (PDF). Nature 439 (7077): 715–718.
Xu X, Norell MA, Kuang X, Wang X, Zhao Q, Jia C 2004. Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroid (PDF). Nature 431 7009: 680–684.
Source: https://pterosaurheresies.wordpress.com/2015/12/27/guanlong-and-dilong-basal-allosaurs-not-basal-tyrannosaurs/
Anyone can join.
Anyone can contribute.
Anyone can become informed about their world.
"United We Stand" Click Here To Create Your Personal Citizen Journalist Account Today, Be Sure To Invite Your Friends.
Before It’s News® is a community of individuals who report on what’s going on around them, from all around the world. Anyone can join. Anyone can contribute. Anyone can become informed about their world. "United We Stand" Click Here To Create Your Personal Citizen Journalist Account Today, Be Sure To Invite Your Friends.
LION'S MANE PRODUCT
Try Our Lion’s Mane WHOLE MIND Nootropic Blend 60 Capsules
Mushrooms are having a moment. One fabulous fungus in particular, lion’s mane, may help improve memory, depression and anxiety symptoms. They are also an excellent source of nutrients that show promise as a therapy for dementia, and other neurodegenerative diseases. If you’re living with anxiety or depression, you may be curious about all the therapy options out there — including the natural ones.Our Lion’s Mane WHOLE MIND Nootropic Blend has been formulated to utilize the potency of Lion’s mane but also include the benefits of four other Highly Beneficial Mushrooms. Synergistically, they work together to Build your health through improving cognitive function and immunity regardless of your age. Our Nootropic not only improves your Cognitive Function and Activates your Immune System, but it benefits growth of Essential Gut Flora, further enhancing your Vitality.
Our Formula includes: Lion’s Mane Mushrooms which Increase Brain Power through nerve growth, lessen anxiety, reduce depression, and improve concentration. Its an excellent adaptogen, promotes sleep and improves immunity. Shiitake Mushrooms which Fight cancer cells and infectious disease, boost the immune system, promotes brain function, and serves as a source of B vitamins. Maitake Mushrooms which regulate blood sugar levels of diabetics, reduce hypertension and boosts the immune system. Reishi Mushrooms which Fight inflammation, liver disease, fatigue, tumor growth and cancer. They Improve skin disorders and soothes digestive problems, stomach ulcers and leaky gut syndrome. Chaga Mushrooms which have anti-aging effects, boost immune function, improve stamina and athletic performance, even act as a natural aphrodisiac, fighting diabetes and improving liver function. Try Our Lion’s Mane WHOLE MIND Nootropic Blend 60 Capsules Today. Be 100% Satisfied or Receive a Full Money Back Guarantee. Order Yours Today by Following This Link.
| Visits: | 1,708,048,367 |
| Stories: | 8,449,401 |
Whistler Blowers, Insiders
