Tag Archives: Teeth

Geoscience seminar this Friday – Janina Rannikko

Dear all,

Janina Rannikko will give the geoscience seminar this Friday (abstract below):


Time: Friday 27.1. at 14.15

Location: D114, Physicum, Kumpula campus



My PhD research is mainly focused on East African suids (pigs) in Plio-Pleistocene. During 8 million years there has been interesting shifts in the faunal and environmental records of Turkana Basin area. The other part of my work has been fundamental research of dental wear, which has been conducted with the chewing machine built here in Helsinki University.


All are welcome!


Tooth Morphogenesis and Differentiation 2016 – First Announcement

Dear Colleagues,

It is our great pleasure to announce the upcoming 12th Tooth Morphogenesis and Differentiation conference, which will be held in Porvoo (Finland), from the 13th to the 18th of June 2016.

The original spirit of the TMD conference has been preserved as all participants will be housed at the conference venue to provide maximum opportunity for sharing their common passion for dental and craniofacial research.

Further information can be found on the conference website:

www.tmd2016.org  The call for abstracts and the opening of registration will be announced later by email and on the website.

Please, share the information with people who might be interested.

Looking forward to seeing you all in Finland.

Best regards,

The organising committee
Frederic Michon (Chairperson)
Jukka Jernvall
Pekka Nieminen

Inferring biological evolution from fracture patterns in teeth

It is hypothesised that specific tooth forms are adapted to resist fracture, in order to accommodate the high bite forces needed to secure, break down and consume food. Three distinct modes of tooth fracture are identified: longitudinal fracture, where cracks run vertically between the occlusal contact and the crown margin (or vice versa) within the enamel side wall; chipping fracture, where cracks run from near the edge of the occlusal surface to form a spall in the enamel at the side wall; and transverse fracture, where a crack runs horizontally through the entire section of the tooth to break off a fragment and expose the inner pulp. Explicit equations are presented expressing critical bite force for each fracture mode in terms of characteristic tooth dimensions. Distinctive transitions between modes occur depending on tooth form and size, and loading location and direction. Attention is focussed on the relatively flat, low-crowned molars of omnivorous mammals, including humans and other hominins and the elongate canines of living carnivores. At the same time, allusion to other tooth forms – the canines of the extinct sabre-tooth (Smilodon fatalis), the conical dentition of reptiles, and the columnar teeth of herbivores – is made to highlight the generality of the methodology. How these considerations impact on dietary behaviour in fossil and living taxa is discussed.


Evolutionary novelty in a rat with no molars

This might be an interesting species for the EvoDevo people.

I saw this article several months ago when I was looking for the diets of vermivore species.
Today I was reading an article of the development of cetacean dentition, and it occurred to me that this rodent might be an interesting species to study. Or perhaps you already knew this one.

“… a new species and genus of shrew-rat from Sulawesi Island, Indonesia that is distinguished from all other rodents by the absence of cheek teeth. Moreover, rather than gnawing incisors, this animal has bicuspid upper incisors, also unique among the more than 2200 species of rodents. Stomach contents from a single specimen suggest that the species consumes only earthworms.”



Cetacean teeth and a new journal

Armfield et al. (2013) Development and evolution of the unique cetacean dentition. PeerJ 1:e24 http://dx.doi.org/10.7717/peerj.24

The evolutionary success of mammals is rooted in their high metabolic rate. A high metabolic rate is sustainable thanks to efficient food processing and that in turn is facilitated by precise occlusion of the teeth and the acquisition of rhythmic mastication. These major evolutionary innovations characterize most members of the Class Mammalia. Cetaceans are one of the few groups of mammals in which precise occlusion has been secondarily lost. Most toothed whales have an increased number of simple crowned teeth that are similar along the tooth row. Evolution toward these specializations began immediately after the time cetaceans transitioned from terrestrial-to-marine environments. The fossil record documents the critical aspects of occlusal evolution of cetaceans, and allows us to pinpoint the evolutionary timing of the macroevolutionary events leading to their unusual dental morphology among mammals. The developmental controls of tooth differentiation and tooth number have been studied in a few mammalian clades, but nothing is known about how these controls differ between cetaceans and mammals that retain functional occlusion. Here we show that pigs, a cetacean relative with regionalized tooth morphology and complex tooth crowns, retain the typical mammalian gene expression patterns that control early tooth differentiation, expressing Bmp4 in the rostral (mesial, anterior) domain of the jaw, and Fgf8 caudally (distal, posterior). By contrast, dolphins have lost these regional differences in dental morphology and the Bmp4 domain is extended into the caudal region of the developing jaw. We hypothesize that the functional constraints underlying mammalian occlusion have been released in cetaceans, facilitating changes in the genetic control of early dental development. Such major developmental changes drive morphological evolution and are correlated with major shifts in diet and food processing during cetacean evolution.


News Flash

This month’s Evolution & Development has several interesting articles (http://onlinelibrary.wiley.com/doi/10.1111/ede.2011.13.issue-6/issuetoc), in particular, an article on odontode evolution and another on digit development in pigs.

Teeth before jaws? Comparative analysis of the structure and development of the external and internal scales in the extinct jawless vertebrate Loganellia scotica
Martin Rücklin, Sam Giles, Philippe Janvier, Philip C. J. Donoghue

Developmental basis of mammalian digit reduction: a case study in pigs
Karen E. Sears, Allison K. Bormet, Alexander Rockwell, Lisa E. Powers, Lisa Noelle Cooper, Matthew B. Wheeler


The End-Permian Mass extinction


Shen, S.-z., Crowley, J. L., Wang, Y., Bowring, S. A., Erwin, D. H., Sadler, P. M., Cao, C.-q., Rothman, D. H., Henderson, C. M., Ramezani, J., Zhang, H., Shen, Y., Wang, X.-d., Wang, W., Mu, L., Li, W.-z., Tang, Y.-g., Liu, X.-l., Liu, L.-j., Zeng, Y., Jiang, Y.-f. & Jin, Y.-g., 2011: Calibrating the End-Permian Mass Extinction.
–ScienceExpress: [doi: 10.1126/science.1213454]

“The end-Permian mass extinction was the most severe biodiversity crisis in earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 Ma, following a decline of 2‰ in δ13C over 90,000 years, and coincided with a δ13C excursion of -5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years, and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.”

Have fun!


Diversity of hypsodont teeth in mammalian dentitions

Just in case somebody finds this interesting… 🙂


Diversity of hypsodont teeth in mammalian dentitions – construction and

von Koenigswald, Wighart

Palaeontographica Abteilung A Band 294 Lieferung 1-3 (2011)
p. 63-94, published: 8/22/2011
9 figures 3 tables


“Hypsodonty, as used here, describes a specific type of tooth with the crown
elongated parallel to the growing axis, a condition which can occur in any
tooth position. Hypsodonty is interpreted as the elongation of specific
ontogenetic phases during tooth development at the cost of all others in a
heterochronic mode. Three parameters are used for differentiation: the
specific elongated ontogenetic phase or phases; the degree of hypsodonty
(increasing hypsodont and euhypsodont); and the kind of abrasion (balanced
wear by an antagonist or free growth). The first parameter is regarded as
the most important one. Although the separation of the four ontogenetic
phases (I – cusps, II – sidewalls, III – dentine surface, and IV –
differentiated roots) is artificial, it allows characterization of the great
diversity of hypsodont teeth in six categories: 1) multicusped hypsodonty
(extended phase I); 2) unicuspid hypsodonty (confluent phases I+II); 3)
sidewall hypsodonty (extended phase II); 4) enamel band hypsodonty (phases
II+III synchronous); 5) partial hypsodonty (phases II+III+IV synchronous);
and 6) dentine hypsodonty (phase III dominant). A synopsis with previously
defined types of hypsodonty is given. The new classification is
comprehensive, opens the view to the construction of hypsodont teeth, and
allows a comparison under evolutionary aspects.”

Too bad that we don’t have rights to download it…