Dinosaur Anatomy 101

[Troodon]

There are a lot of experienced dinosaur collectors out there but for the newbie I thought a topic on the anatomy of bones and teeth would be beneficial, in plain english. Avoids reading pdf's that are difficult to get through the technical terms.

Orientation

Skeleton

The specific sketal structure of a dinosaur varies between theropod and herbivore but the major elements are typical.

Skulls of dinosaurs are not comprised of a single bone but many elements

See the osteology of a Trex skull on page 2

 

The holes in the skull are identified as follows

Theropod Teeth

Theropod teeth are widely collected let's look at their anatomy and nomenclature

Tooth Orientation

Apical- The direction from the cervix to the apex (Fig. 1C, E).

Basal- The direction from the apex to the cervix (Fig. 1C, E).

Mesial- The direction towards the jaw midline, center (Fig. 1C). Mesial can refer also to the surface facing the jaw midline, center.

Distal- This term is used slightly differently for teeth versus denticles. For teeth, distal refers to the direction away from the jaw center and towards the posterior end of the jaw (Fig. 1C). For denticles, distal refers to the direction away from the crown, from the denticle base to the denticle apex (Fig. 1E).

Proximal- From the denticle apex to the base, proximal refers to the direction towards the crown ( Fig. 1E).

Labial- The surface or direction pointing from the skull outwards, thus towards the lips or cheeks ( Fig. 1D).

Lingual- The surface and direction towards the skull midline, thus facing the tongue ( Fig. 1D).

Tooth Situation and Position

Isolated Tooth- Tooth shed or non-articulated with the toothbearing bone. This is what collectors typically purchase.

Shed Tooth- Tooth lost while alive,, either falling out due to the eruption of the replacement tooth or when processing food (e.g., biting, impaling, shearing, chewing), and therefore only preserving the crown and the basal-most part of the root.

In Situ Tooth-Tooth within the alveolus of the tooth-bearing bone.

Erupted Tooth- Tooth that grew outside the tooth-bearing bone, thus fully visible in the mouth.

Unerupted Tooth- Tooth within the alveolus and still inside the jaw, and therefore not visible or only partially visible in the mouth.

Premaxillary Tooth - Tooth in front of the upper jaw, typically four would exist in a theropod

Maxillary Tooth - Tooth in the upper jaw that follow the Premaxillary teeth.

Dentary Tooth- Tooth in the lower jaw

Tooth Anatomy

Crown (co) Portion of the tooth covered with enamel, typically situated above the gum and protruding into the mouth

Root (ro) Portion of the tooth beneath the gum and embedded in an alveolus or an open alveolar groove

[Troodon]

The skeleton is divided into into three sections: cranial (the head); axial (the vertebral column and ribs and appendicular (the limbs). Since most collectors focus on the limbs lets see a little more detail than before.

This is an example of a Ceratopsian. .

This is the forelimb ( the arm )

.

The hand is next but its more properly called the manus. It's composed of carpals (wrist bones) metacarpals (MC) and phalanges (single one called phalanx) (commonly referred to as finger bones) the last one is called an ungual or claw. Each digit is numbered starting at the thumb. The thumb I (note Roman numeral), the index finger II, middle finger III, ring finger IV, and pinkie V.

The phalanges are numbered by digit (I-V) as well as their position relative to the metacarpals (given by an Arabic numeral)

Hands of dinosaurs are all different but all follow a similiar scheme

This is the hindlimb (the leg)

The foot is next but more properly referred to as the pes. It's configured in a slightlydifferent way. Instead of metacarpals we have metatarsals (MT)

Theropods

Here is an example of a theropod (Ornithomimid) hand and foot. Most hands have 3 digits and most feet have four major digits and a vestige of a digit called a splint but certain theropods like Ornithomimids have only 3 missing Digit I. Tyrannosaur hands, depending on the species, can have two major digits and a vestige digit.

Most theropod feet look like this with Digit I also know as the dew claw. The illustration is that of an Allosaurus foot. The number of bones in each digit is typically the same with all theropods.

Hadrosaurs

Hadrosaurs have a very unusual hands "manus" and all species are slightly different. Sorry for the poor illustrations.

Their feet are pretty simple and only have three digits

Edited August 25, 2016 by Troodon

[Troodon]

Raptor killing claws:

Finding or buying a Raptor killing claw is as good as it gets. Sellers are quick to offer any recurved claw as one. So how can you tell if it's one, they can easily get confused with hand claws that have similiar features? Killing claws are typically found on small or intermediate size Dromaeosaurid type dinosaurs and are always on Digit II, so one per foot. They are typically recurved but exceptions exist.

A foot of a raptor is in show in the attached illustration. Note how very different digit I, III & IV claws are.

So how can you differentiate the between a hand and killing claw. The easiest for a novice is to look at the proximal end, that's the side that attaches to the phalanx digit, it has a different flexor attachment point. With a hand claw we see a small "half moon" attachment point while on a foot claw the flexor attachment is usually the full width of the back end. There are exceptions but you can follow this as a general practice.

Foot Claw

Hand Claw

Reference material is a must for collectors. Here are some that I rely on, my copies are well worn.

http://www.thefossilforum.com/index.php?/topic/66551-best-dinosaur-books/

Inside working on a theropod claw. This is Allosaurus

Edited August 26, 2016 by Troodon

[Nimravis]

There are a lot of experienced dinosaur collectors out there but for the newbie I thought a topic on the anatomy of bones and teeth would be beneficial, in plain english. Avoids reading pdf's that are difficult to get through the technical terms.

Orientation

anatomicalorientation (1).jpg

Skeleton

The specific sketal structure of a dinosaur varies between theropod and herbivore but the major elements are typical.

bone+guide (1).jpg

Skulls of dinosaurs are not comprised of a single bone but many elements

skull+bones (1).jpg

The holes in the skull are identified as follows

skull+holes.jpg

Theropod Teeth

Theropod teeth are widely collected let's look at their anatomy and nomenclature

Screenshot_20160825-074708.jpg

Tooth Orientation

Apical—The direction from the cervix to the apex (Fig. 1C, E).

Basal—The direction from the apex to the cervix (Fig. 1C, E).

Mesial—The direction towards the jaw midline, center (Fig. 1C). Mesial can refer also to the surface facing the jaw midline, center.

Distal—This term is used slightly differently for teeth versus denticles. For teeth, distal refers to the direction away from the jaw center and towards the posterior end of the jaw (Fig. 1C). For denticles, distal refers to the direction away from the crown, from the denticle base to the denticle apex (Fig. 1E).

Proximal—From the denticle apex to the base, proximal refers to the direction towards the crown ( Fig. 1E).

Labial—The surface or direction pointing from the skull outwards, thus towards the lips or cheeks ( Fig. 1D).

Lingual—The surface and direction towards the skull midline, thus facing the tongue ( Fig. 1D).

Tooth Situation and Position

Isolated Tooth—Tooth shed or non-articulated with the toothbearing bone.

Shed Tooth—Tooth lost while alive,, either falling out due to the eruption of the replacement tooth or when processing food (e.g., biting, impaling, shearing, chewing), and therefore only preserving the crown and the basal-most part of the root.

In Situ Tooth—Tooth within the alveolus of the tooth-bearing bone.

Erupted Tooth—Tooth that grew outside the tooth-bearing bone, thus fully visible in the mouth.

Unerupted Tooth—Tooth within the alveolus and still inside the jaw, and therefore not visible or only partially visible in the mouth.

Premaxillary Tooth - Tooth in front of the upper jaw, typically four would exist in a theropod

Maxillary Tooth - Tooth in the upper jaw that follow the Premaxillary teeth.

Dentary Tooth- Tooth in the lower jaw

Tooth Anatomy

Crown (co)—Portion of the tooth covered with enamel, typically situated above the gum and protruding into the mouth

Root (ro)—Portion of the tooth beneath the gum and embedded in an alveolus or an open alveolar groove

Screenshot_20160825-082438.jpg

Great info - thanks much.

[FossilDudeCO]

YAY FOR TROODON!!

[CraigHyatt]

Can't thank you enough for this.

[Bguild]

Very cool! Thanks for the info. There are some terms in here that I always mix up. This should help. Very useful diagrams.

[JohnBrewer]

Very very useful, thank-you!

[siteseer]

There's a player on the Los Angles Rams who would benefit greatly from this information. He doesn't think dinosaurs ever lived (how do they know which bones go together?) but he's keeping an open mind about the existence of mermaids.

I've always gone by the old line about the hip bone being connected to the thigh bone, the thigh bone's connected to the shin bone...

Jess

The skeleton is divided into into three sections: cranial (the head); axial (the vertebral column and ribs and appendicular (the limbs). Since most collectors focus on the limbs lets see a little more detail than before.

This is an example of a Ceratopsian. .

This is the forelimb ( the arm )

forelimb.png.

The hand is next but its more properly called the manus. It's composed of carpals (wrist bones) metacarpals (MC) and phalanges (single one called phalanx) (commonly referred to as finger bones) the last one is called an ungual or claw. Each digit is numbered starting at the thumb. The thumb I (note Roman numeral), the index finger II, middle finger III, ring finger IV, and pinkie V.

The phalanges are numbered by digit (I-V) as well as their position relative to the metacarpals (given by an Arabic numeral)

Hands of dinosaurs are all different but all follow a similiar scheme

manus2.png

This is the hindlimb (the leg)

hindlimb_labeled1.png

The foot is next but more properly referred to as the pes. It's configured in a slightlydifferent way. Instead of metacarpals we have metatarsals (MT)

pes.png

Here is an example of a theropod (Ornithomimid) hand and foot. Most hands have 3 digits and most feet have four major digits and a vestige of a digit called a splint but certain theropods like Ornithomimids have only 3 missing Digit I. Tyrannosaur hands, depending on the species, can have two major digits and a vestige digit.

Screenshot_20160825-114453.jpg

Most theropod feet look like this with Digit I also know as the dew claw. The illustration is that of an Allosaurus foot. The number of bones in each digit is typically the same with all theropods.

Screenshot_20160825-115135_20160825115331479.jpg

Edited August 25, 2016 by siteseer

[izak_]

I can't describe how helpful this is! Thanks so much. Its great.

[Dracorex_hogwartsia]

Nice job! Great information all in one spot.

[sandgroper]

This is fantastic mate, thanks for taking the time to put this together, it will help me enormously and, I'm sure, plenty of others.

Edited August 25, 2016 by sandgroper

[Pagurus]

Thanks for sharing your anatomy lesson with us! Concise and easy on the eyes. Wonderful.

[snolly50]

"There is nothing so stupid as the educated man if you get him off the thing he was educated in." - Will Rogers

Yep, describes me. That's why this Forum is so great. Posts like this go a long way to correcting that sad state. Like most autodidacts, I know a lot; but being self taught, I am woefully ill-informed on the basics. Folks interested in a subject, who are self-instructed, tend to grab on to the exciting "big concepts." That's great, but it leaves fundamentals lacking.

Thanks for this truly helpful post. Yeah, I "know" most of this info already; but it's not ingrained as it should be. Additional exposure has got to be helpful.

[Susan from PA]

Thanks Troodon! I'm printing this for my first trip to the Hell Creek Formation!

[Troodon]

Appreciate all the great feedback.

Susan I hope you get an opportunity to use this information on your upcoming dig, good luck.

Jess you should send that Ram linebacker to the LA museum or just back to St.Louis.

Snolly what can I say great summary thank you.

[Raggedy Man]

"But its a mermaid, though We find different species in the water every day."

Rofl....wow. I wonder if he likes fishsticks...lol.

Edited August 26, 2016 by Raggedy Man

[LordTrilobite]

I've always gone by the old line about the hip bone being connected to the thigh bone, the thigh bone's connected to the shin bone...

Jess

Secret of Monky Island reference?

"There is nothing so stupid as the educated man if you get him off the thing he was educated in." - Will Rogers

Yep, describes me. That's why this Forum is so great. Posts like this go a long way to correcting that sad state. Like most autodidacts, I know a lot; but being self taught, I am woefully ill-informed on the basics. Folks interested in a subject, who are self-instructed, tend to grab on to the exciting "big concepts." That's great, but it leaves fundamentals lacking.

Thanks for this truly helpful post. Yeah, I "know" most of this info already; but it's not ingrained as it should be. Additional exposure has got to be helpful.

I completely agree.

Edited August 26, 2016 by LordTrilobite

[Troodon]

Added pg 3 Raptor Killing Claws

Edited page

Edited August 26, 2016 by Troodon

[ynot]

Thanks for this wonderful and informative article!!!

Tony

[PFOOLEY]

This is a wonderful compilation of information! 

 

Thank you, Frank.

[Ludwigia]

This is certainly a very important thread to be bookmarked. Thanks very much for posting this!

[abach292]

Useful! Booking marking this for reference.

[Troodon]

Vertebrae

 

Diggers in the Hell Creek/Lance Formations often find vertebra and you see them sold on web sites or auction houses.   A vertebra 101 discussion can help collectors better understand what they are seeing.    Identifying isolated vertebrae like teeth is not an easy task.   The more complete the specimen is greater the odds are to properly identify it.  Identification based on just looking at the centrum without processes is extremely difficult and prone to error

 

Lets first look at dinosaurs vertebra anatomy.   I did not find a lot of good images out there and decided on this one.  

The important terms are:

Types of Vertebra: Cervical, Dorsal, Sacral and Caudal.  You can see their location on the very first page second photo. 

Centrum: The body of the vertebra 

Neural spine:  The process projecting upward sometimes called the dorsal spine.  

Transverse Process - There is one on each side and they run lengthwise

Neural Canal: The opening in the vertebra where the spinal cord runs

 

 

 

 

The most common vertebrae found in the Hell Creek/Lance Formations are Hadrosaur (Edmontosaurus) and Ceratopsian (Triceratops).   Distinguishing between the two can be difficult but again the more complete the specimen the better opportunity for success.   The simplest way to describe the difference when looking at from an end is that a Hadrosaur is more box (rectangular) shaped while a Ceratopsian is rounder.  The neural spines depending on location on the column can also be different.   The next two photos are those of a distal caudal and you can see the difference.

 

 

Higher up on the tail closer to the hip its gets more difficult but you still can see the difference.

 

Here are two classic illustrations of a Hadrosaur followed buy a Triceratops

 

 

[Troodon]

One type of vertebrae that is commonly confused by sellers is Pachycephalosaurid versus Thescelosaurus.   The centrums are very similar and without the processes its difficult to tell them apart.  Dorsal vertebra can be difficult but with Caudal ones you can differentiate between the two.

Attached photos can help you see the difference but the neural spine on Thescelosaurs pitches to the distal end of the tail while the Pachy are mostly upright.  Thescelosaurus can also have a well definded edge in the middle of the centrum/

Thescelosaurus

 

 

 

Pachycephalosaurus