Related Experiment Video
Updated: May 30, 2026
08:02
Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
Published on: May 7, 2016
First tooth-set outside the jaws in a vertebrate.
John A Finarelli1, Michael I Coates
1Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA. john.finarelli@uchicago.edu
Proceedings. Biological Sciences
|July 22, 2011
Summary
This study describes the unique teeth and toothplates of Chondrenchelys problematica, an early holocephalan. Findings reveal novel gnathostome dental evolution and challenge existing classifications of extinct shark relatives.
Area of Science:
- Paleontology
- Evolutionary Biology
- Comparative Anatomy
Background:
- Holocephalans (chimaeras) are increasingly important in gnathostome evolutionary studies.
- Understanding early holocephalan dentition provides insights into vertebrate evolution.
- Chondrenchelys problematica is an early holocephalan fossil crucial for evolutionary analysis.
Purpose of the Study:
- To provide the first complete description of Chondrenchelys problematica teeth and toothplates.
- To present the first unambiguous evidence of extra-mandibular dentition in a gnathostome.
- To investigate holocephalan toothplate ontogeny and its evolutionary implications.
Main Methods:
- Detailed morphological analysis of Chondrenchelys problematica fossil specimens.
- Comparative analysis of holocephalan dentition with other gnathostomes.
- Phylogenetic analysis to assess the impact of findings on chondrichthyan clades.
Main Results:
- Complete description of Chondrenchelys problematica dentition, including novel extra-mandibular teeth.
- Demonstration that holocephalan toothplate ontogeny fundamentally differs from extant gnathostomes.
- Evidence suggesting the monophyly of the extinct chondrichthyan clade Petalodontiformes is challenged.
Conclusions:
- Chondrenchelys problematica offers a new perspective on the evolution of shark-like fish dentitions.
- The study expands the known diversity of gnathostome dental morphologies.
- Findings shed light on extinct chondrichthyan ecomorphs lost after the end-Devonian extinctions.
Related Concept Videos
01:15Teeth
The formation of teeth, also known as odontogenesis, is a complex process that begins in utero, around the sixth week of embryonic development. There are three stages to this process: the bud stage, the cap stage, and the bell stage.
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
In the bud stage, the tooth germ (an aggregation of cells) starts to form in the developing jawbone. During the cap stage, the tooth germ differentiates into enamel organ, dental papilla, and dental sac, which will later develop into the tooth's enamel, dentin and...
01:21Tooth Anatomy
The human tooth enables us to eat a variety of foods, speak clearly, and even aid in shaping our faces. Teeth are composed of various elements that work together. Here's a detailed look at the anatomy of a human tooth.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
01:29Bone Formation by Intramembranous Ossification
Intramembranous ossification is one of the two processes involved in the development of bones within an embryo. The flat bones of the face, most of the cranial bones, and the clavicles are formed via this process. During intramembranous ossification, the bones develop directly from sheets of undifferentiated mesenchymal connective tissue.
The process begins when mesenchymal cells in the embryonic skeleton gather together and differentiate into osteogenic cells, which then develop into...
The process begins when mesenchymal cells in the embryonic skeleton gather together and differentiate into osteogenic cells, which then develop into...
01:11Oral Cavity
The oral cavity, or the mouth, is a complex structure in humans that plays a vital role in our day-to-day lives. Its role is not only in chewing and swallowing food; it also plays a role in speech and facial expressions.
Teeth: The teeth are the hardest structures in our bodies. Humans have two sets of teeth throughout their lifetime: deciduous (baby) teeth and permanent teeth. Each tooth consists of several parts: the crown (visible part), the root (embedded in the jaw), enamel (hard outer...
Teeth: The teeth are the hardest structures in our bodies. Humans have two sets of teeth throughout their lifetime: deciduous (baby) teeth and permanent teeth. Each tooth consists of several parts: the crown (visible part), the root (embedded in the jaw), enamel (hard outer...
01:27Cranial Bones: Lateral View
The lateral view of the cranium is dominated by temporal, sphenoid, and ethmoid bones.
The temporal bone forms the lower lateral side of the skull. The temporal bone is subdivided into several regions. The flattened upper portion is the squamous portion of the temporal bone. Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. Posteriorly is the mastoid portion of the temporal bone. Projecting...
The temporal bone forms the lower lateral side of the skull. The temporal bone is subdivided into several regions. The flattened upper portion is the squamous portion of the temporal bone. Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. Posteriorly is the mastoid portion of the temporal bone. Projecting...
01:30Neurulation
Neurulation is the embryological process which forms the precursors of the central nervous system and occurs after gastrulation has established the three primary cell layers of the embryo: ectoderm, mesoderm, and endoderm. In humans, the majority of this system is formed via primary neurulation, in which the central portion of the ectoderm—originally appearing as a flat sheet of cells—folds upwards and inwards, sealing off to form a hollow neural tube. As development proceeds, the anterior...