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RESEARCH ARTICLE
Analysis of enamel defects in a cave bear maxillary molar, with
remarks on incremental markings in bear enamel
Uwe Kierdorf
1
| Dean Konjevi
c
2
| Siniˇ
sa Radovi
c
3
| Miljenko Bujani
c
2
|
Horst Kierdorf
1
1
Department of Biology, University of
Hildesheim, Hildesheim, Germany
2
Faculty of Veterinary Medicine, University of
Zagreb, Zagreb, Croatia
3
Institute for Quaternary Palaeontology and
Geology, Croatian Academy of Sciences and
Arts, Zagreb, Croatia
Correspondence
Uwe Kierdorf, Department of Biology,
University of Hildesheim, Universitätsplatz
1, 31141 Hildesheim, Germany.
Email: uwe.kierdorf@uni-hildesheim.de
Abstract
The paper discusses the formation of an enamel defect in the crown of a cave bear
(Ursus spelaeus sensu lato) left maxillary second molar (M
2
), based on macroscopic
and microscopic analysis. The tooth belongs to a cranium recovered from the
Cerovac caves in Croatia that exhibits a partially healed, depressed lesion in the left
squama frontalis and a further lesion in the left maxilla associated with loss of the
M
1
. Microscopic inspection demonstrated an accentuated incremental line in both
enamel and dentin of the left M
2
. It is suggested that in the defect area the outer
enamel had been posteruptively lost along the accentuated line in the enamel that
constituted a zone of reduced mechanical resistance. Presence of enamel hypoplasia
in both M
2
indicated that these developmental lesions reflect a systemic stress event
during crown formation of the teeth. The underlying cause of this stress is assumed
to have been a trauma to the skull that caused the lesion in the left squama frontalis.
It is further suggested that a later trauma to the left maxilla had led to the loss of the
left M
1
and the flaking-off of enamel along the accentuated incremental line in the
left M
2
. The defect in the left M
2
is thus diagnosed as the result of a developmental
lesion during crown formation, related to systemic stress due to a skull trauma, fol-
lowed by posteruptive damage from a second traumatic impact. In addition to recon-
structing the formation of the defect in the crown of the left M
2
, the paper, for the
first time, describes daily and subdaily incremental markings in ursid enamel and pro-
vides preliminary information on enamel secretion rate in a cave bear molar.
KEYWORDS
animal paleopathology, enamel defects, enamel incremental markings, Pleistocene, trauma,
Ursidae
1|INTRODUCTION
The cave bear (Ursus spelaeus sensu lato) is a prominent member of
the Eurasian Pleistocene megafauna (Kurtén, 1976; Rabeder
et al., 2000; Stuart, 2021). The species Ursus spelaeus was erected in
1794 by J. C. Rosenmüller in his doctoral dissertation
(Rosenmüller, 1794). Cave bear remains had already previously been
studied (Esper, 1774), however, without assigning them to a new spe-
cies. The diverse Late Pleistocene cave bear complex evolved from
the Middle Pleistocene Ursus deningeri and comprises several
Received: 8 March 2024 Revised: 5 May 2024 Accepted: 6 May 2024
DOI: 10.1002/oa.3309
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited and is not used for commercial purposes.
© 2024 The Authors. International Journal of Osteoarchaeology published by John Wiley & Sons Ltd.
Int J Osteoarchaeol. 2024;e3309. wileyonlinelibrary.com/journal/oa 1of10
https://doi.org/10.1002/oa.3309
morphologically and genetically distinct forms, separated at the spe-
cies and subspecies levels (Baca et al., 2016; Barlow et al., 2018;
Gretzinger et al., 2019; Rabeder et al., 2000). Different lines of evi-
dence indicate that cave bears were herbivorous, with a high amount
of high-quality herbaceous plants in their diet (Bocherens, 2019;
Pacher & Stuart, 2009; Rabeder et al., 2000; Terlato et al., 2019). Cave
bears hibernated in caves, and large numbers of their bones have
been found in caves across Europe (Grandal-d'Anglade et al., 2019;
Kurtén, 1976).
Cave bear extinction occurred between about 28 to 25 kyr BP
across most of its range, broadly coinciding with Greenland stadial
3, the coldest phase of the last glacial (Baca et al., 2016; Pacher &
Stuart, 2009; Terlato et al., 2019). Younger dates of 24,200–
23,500 cal yr BP for skeletal remains from NE-Italy indicate somewhat
longer survival in refugia with more favorable climatic conditions
(Terlato et al., 2019). Cave bear extinction was preceded by a decline
in population size that started approximately 25,000 years before its
final disappearance (Stiller et al., 2010). The ultimate cause(s) of
extinction are a matter of debate (Kurtén, 1976; Stuart, 2021). Some
authors suggest that vanishing of the cave bear was caused by cli-
matic deterioration and associated decreased productivity of the veg-
etation, with extinction being preceded by range fragmentation and
formation of isolated small subpopulations (Baca et al., 2016;
Pacher & Stuart, 2009). Others have concluded that, in combination
with climatic deterioration, increasing human pressure was a major
factor leading to cave bear extinction (Gretzinger et al., 2019; Stiller
et al., 2010; Terlato et al., 2019).
The large number of skeletal remains available for study facili-
tated numerous studies on pathological changes or developmental
abnormalities in cave bear bones and teeth (Abel & Kyrle, 1931;
Capasso, 1998; Capasso & Caramiello, 1999; Esper, 1774;
Kurtén, 1976; Marciszak et al., 2024; Nowakowski & Stefaniak, 2015;
Rabeder et al., 2000; Tasnádi-Kubacska, 1962; Toledano et al., 2010;
Withalm, 2004). Mostly, the pathological specimens were analyzed
only macroscopically, and rather few studies addressed histological
and/or radiological aspects of the skeletal and dental lesions
(Capasso, 1998; Marciszak et al., 2024; Nowakowski &
Stefaniak, 2015; Toledano et al., 2010).
The permanent dentition of the cave bear comprises 30 teeth,
the dental formula being I 3/3, C 1/1, P1/1, M 2/3 (Thenius, 1989;
van Heteren et al., 2014). Compared with other ursids, the number of
premolars is reduced, with only the P4 remaining. Cave bear molars
are large with rather complex occlusal surfaces, regarded as an adap-
tation to the processing of plant material (Rabeder et al., 2000). A
study by von Koenigswald (1992) revealed that, despite its herbivo-
rous diet, enamel structure of the cave bear is similar to that of other
Carnivora. In line with this statement, Loch et al. (2022) recently
described the enamel structure in the carnivorous polar bear (Ursus
maritimus) as being very similar to that of the cave bear.
The present paper describes and analyzes enamel defects in a
maxillary second molar (M
2
) of a cave bear cranium from a fossil site
in Croatia. Additionally, information on incremental markings in ursid
enamel is given for the first time.
2|MATERIALS AND METHODS
2.1 |The fossil site
The studied tooth originates from a cave bear cranium recovered from
the Cerovac caves (Cerovaˇ
cke pe
cine) located in the municipality of
Graˇ
cac (county of Zadar, Croatia). The three karst caves (lower, middle
and upper Cerovac cave) are situated on the NE slope of Mt. Crnopac
in the Velebit mountain range and have been studied in different cam-
paigns between 1913 and 2019 (Kureˇ
ci
c et al., 2021; Malez, 1965).
The caves yielded a huge amount of cave bear skeletal remains, repre-
senting individuals from all age classes that used the caves for hiber-
nation over many generations (Malez, 1965). Based on our current
understanding of Late Pleistocene cave bear phylogeography
(Gretzinger et al., 2019), it is assumed that the cave bears from the
Cerovac site belonged to the Ursus ingressus clade within the
U. spelaus sensu lato complex.
2.2 |Cave bear cranium CER-2962
The cave bear cranium with collection number CER-2962 is housed in
the Institute for Quaternary Paleontology and Geology of the
Croatian Academy of Sciences and Arts in Zagreb. The specimen has
been initially described and depicted by Malez (1965); however, with-
out mention of the dental pathology. The cranium is fragmentary with
both nasal bones and portions of both zygomatic arches missing, and
its facial portion is slightly deviated to the left (Figure 1a). The mandi-
ble is missing. The cranium exhibits an impression with rounded mar-
gins in the region of the left squama frontalis, with a thinning and
localized perforation of the bone (Figure 1a). This defect is diagnosed
to represent a partially healed depressed lesion of the skull roof. Adja-
cent to the impression, the interfrontal suture is bent to the left
(Figure 1a).
Inspection of the cranium indicated that the individual had
originally possessed a complete and fully erupted permanent upper
dentition. Using the age scoring system of Stiner (1998), cranium
CER-2962 was assigned to an individual of late juvenile age at death
(age state III). All six incisors are missing; however, the fact that their
alveoli are intact and unfilled indicates that these teeth were lost
postmortem. Of the remaining teeth, only the left M
1
is missing
(Figure 1b). A larger portion of the buccal wall of the M
1
alveolus has
been resorbed, and the bone surrounding this defect zone shows
increased porosity indicative of an inflammatory process (Figure 1b).
The M
1
alveolus shows minor osseous infilling (insert in Figure 1b).
2.3 |Imaging of the cheek teeth and processing of
the left M
2
First, digital images of the cheek teeth of cranium CER-2962 were
obtained. Following removal from the maxilla, which caused some
damage to its root and crown (Figure 2a,b), the left M
2
was
2of10 KIERDORF ET AL.
photographed with a digital microscope (VHX 7000, Keyence, Osaka,
Japan). Subsequently, the tooth was embedded in epoxy resin
(Biodur
®
E12, Biodur Products, Heidelberg, Germany) and longitudi-
nally (axio-buccopalatally) sectioned through its mesial (anterior) lobe
(Figure 3a). The section surface of the mesial segment was manually
smoothed using a graded series of silicon carbide sandpapers, fol-
lowed by polishing on a motorized rotary polisher (Labopol 5, Struers,
Ballerup, Denmark) using a 3 μm diamond suspension and a 0.3 μm
alumina slurry.
The polished section surface of the tooth was viewed under
reflected light in the VHX 7000 digital microscope. Subsequently, the
uncoated surface was examined in a scanning electron microscope
(SEM, Evo Ma 15, Carl Zeiss, Oberkochen, Germany), operated in the
backscattered electron (BSE) mode at 20 kV. Gray level variation in
BSE images of topographically flat mineralized tissues reflects local
variation in mineral content, with brighter gray levels characterizing
areas of higher, and darker levels areas of lower mineral content
(Boyde & Jones, 1983; Skedros et al., 1993). For better visualization,
the gray-scale images were converted to pseudo-color images using
the 16-colors lookup table of ImageJ (NIH, Bethesda, USA). For that,
the 256 gray values from black (0) to peak white (255) were converted
to 16 bands of equal width, each represented by a different color.
Following acquisition of the BSE images, the mesial tooth slab
was mounted on a microscopic slide with its polished side down, using
the epoxy resin as glue. A thin ground section of about 50 μm thick-
ness was then produced by grinding with a graded series of sandpa-
pers and a final polishing step using a leather cloth and a dry-polishing
compound. The cover-slipped section was viewed and photographed
with the Keyence VHX 7000 digital microscope and a Zeiss Axioskop
2 plus microscope equipped with an Axiocam 503 color digital camera
(Carl Zeiss, Oberkochen, Germany), using plain transmitted light with
phase contrast enhancement and linearly polarized transmitted light.
To achieve the same orientation as the reflected light and SEM images
of the block surfaces, the light microscopic images of the ground sec-
tions were horizontally mirrored. All image processing was done using
Adobe Photoshop software (Adobe Inc., San Jose, USA).
3|RESULTS
The mesiobuccal cusp (paracone) of the left M
2
of cranium CER-2962
exhibited a large enamel defect that extended along the occlusal half
of the buccal side of the tooth crown (Figure 2a). A pronounced ledge
separated the defect area from the adjacent crown portion
(Figures 2a and 3a–c). Further distally, the zone of reduced enamel
thickness was bordered both occlusally and cervically by thicker
enamel (Figure 2a). On macroscopic inspection, the palatal enamel of
the tooth appeared normal (Figure 2b), but smaller defects were
observed in its occlusal enamel. In the right M
2
, numerous pit-type
enamel defects, some of which had become confluent, were present
in the tip regions of the paracone and metacone (Figure 2c). The
affected cusp areas exhibited a brownish staining of their enamel sug-
gestive of hypomineralization (Figure 2c).
Microscopic analysis of the polished block surface and the thin
section of the left M
2
revealed the presence of an accentuated incre-
mental line in the enamel (Figures 3b–dand 4a,b). Along this line, the
FIGURE 1 Cave bear cranium CER-2962 from the Cerovac caves. (a) Dorsal view of the cranium showing the healed depressed lesion (arrow)
in the left squama frontalis. Arrowhead: deviation in the course of the interfrontal suture. (b) Left lateral view of the cranium showing P
4
,M
2
and
empty M
1
alveolus. Note defect in M
1
alveolar wall (arrow) and signs of inflammation (increased porosity) of the surrounding alveolar bone. Inset
image: ventral view of the cranium showing minor osseous infilling (arrow) of the M
1
alveolus.
KIERDORF ET AL.3of10
continuity of the enamel prisms was disrupted (Figures 3d and 4a–c).
Light microscopic inspection at higher magnification demonstrated a
zig-zag pattern at the border between an inner zone of prismatic
enamel and the externally adjacent accentuated incremental line that
lacked a prismatic structure (Figure 4c). The accentuated incremental
line in the enamel corresponded to an accentuated line in the dentin,
which was characterized by interglobular spaces, that is, zones of
unmineralized dentin matrix (Figure 3d). The accentuated lines in
enamel and dentin converged towards the enamel-dentin-junction
(EDJ). The line in dentin met the EDJ slightly further cervically than
that in enamel, reflecting the earlier onset of dentin formation com-
pared with enamel formation.
In places, the enamel bordering the defect zones in the crown
exhibited a convexly rounded, smooth surface (Figure 4a,b). In other
places, the defect margins and the defect bottom exhibited the
uneven, ragged topography of a fracture plane, indicating that the
outer enamel had flaked off along the accentuated incremental line.
The position of the fracture plane relative to the accentuated incre-
mental line indicated that some enamel located internal to the line
had also been lost (Figure 4a). The enamel defects were partly
occluded by mineralized deposits, representing dental calculus and/or
sediment (Figure 4b). The peripheral dentin of the left M
2
showed
some areas affected by diagenesis that on the polished block surface
presented as dark zones when viewed under reflected light
(Figure 3b).
Light microscopic inspection of the ground section also revealed
some normal structural details of the enamel. An inner enamel zone of
varying width was characterized by pronounced Hunter-Schreger
FIGURE 2 Maxillary cheek teeth of
cranium CER-2962. (a) Buccal view of the
left M
2
. Arrow: extended defect in the
buccal enamel of the paracone, white
arrowhead: crown-root border, black
arrowhead: defect of enamel caused
during tooth removal. Note damage also
to the root caused by tooth removal.
(b) Palatal view of the left M
2
. Arrow:
crown-root border. Note damage to the
root caused by removal. (c) Bucco-occlusal
view of right maxillary cheek teeth (P
4
,
M
1
,M
2
). Arrow: pit-type defects in buccal
enamel of the M
2
paracone, arrowhead:
crown-root border of M
2
. Note brownish
staining of enamel at the cusp tips of the
cheek teeth. [Colour figure can be viewed
at wileyonlinelibrary.com]
4of10 KIERDORF ET AL.
FIGURE 3 Legend on next page.
KIERDORF ET AL.5of10
bands (Figure 3c), while the prisms in the outer zone showed little or
no decussation. At higher magnifications, regular incremental mark-
ings were observed in the enamel. These markings consisted (1) of
lines (laminations) that crossed the prism course at oblique angles and
(2) of prism cross-striations between consecutive laminations. In sec-
tions viewed under polarized light, the cross-striations presented as
alternating bright and dark bands along the course of individual prisms
(Figure 4d). Given the nature of laminations as daily incremental mark-
ings (Emken et al., 2021; Kierdorf et al., 2013), the enamel secretion
rate for the outer lateral enamel zone depicted in Figure 4d was
reconstructed to be in the range of 17 to 19 μm/day.
4|DISCUSSION
The observations on the left M
2
of cranium CER-2962 allow some
conclusions regarding the formation of the dental defects. The find-
ings indicate that a pronounced systemic stress event affected amelo-
blasts as well as odontoblasts, causing the simultaneous formation of
the accentuated incremental lines in enamel and dentin. The presence
of such lines and the occurrence of interglobular dentin along the
course of accentuated incremental lines in the dentin are indicative of
developmental disturbances during tooth formation (Hillson, 2014;
Kierdorf et al., 2021; Richter et al., 2010). We assume that the dis-
turbed enamel and dentin formation in the cave bear molar was
caused by the trauma to the frontal bone, and possible sequelae of
this event.
It has previously been suggested that the lesion in the left squama
frontalis of cranium CER-2962 was inflicted by a Paleolithic hunter
(Malez, 1965). However, this author did not provide data to support
his hypothesis. A recent study on cave bear skeletal remains from the
lower Cerovac cave provided no evidence of bone modifications by
hominins (Kureˇ
ci
c et al., 2021). We therefore tend to reject the sce-
nario proposed by Malez (1965) and instead favor two other possible
explanations. Thus, the lesion could represent a bite wound from an
interspecific or intraspecific aggressive encounter. Several cases of
bite damage to the frontals and other skull bones of cave bear have
been reported and were attributed to attacks by either large
predators, mostly cave lions (Panthera leo spelaea), or conspecifics
(Capasso, 1998; Diedrich, 2011,2014; Nowakowski & Stefaniak,
2015). Like in the case reported here, some of these lesions show
signs of healing. Alternatively, the lesion in the frontal bone of CER-
2962 could represent a depressed fracture caused by a larger piece of
host rock or a speleothem that had dropped from the cave ceiling and
hit the cave bear's head.
The topography of the internal border of the accentuated incre-
mental line in the enamel of the left M
2
denotes an abrupt detach-
ment of the secretory ameloblasts from the surface of the forming
enamel due to the stress event. In mammals, fully active secretory
ameloblasts possess two sites of matrix secretion at their distal cell
extension, which is referred to as the Tomes' process (Nanci, 2018).
While interprismatic (interrod) enamel is formed adjacent to the proxi-
mal portion of the Tomes' process, the prisms (rods) are formed in
relation to the distal portion of this process that protrudes into the
enamel layer (Nanci, 2018). When the sheet of secretory-stage amelo-
blasts is detached from the surface of the forming enamel, this leaves
a series of pits, each of which was previously occupied by a
distal Tomes' process. The zig-zag (“picket-fence”) topography
(Boyde, 1989) observed along the internal border of the accentuated
incremental line in the longitudinally sectioned left M
2
of cranium
CER-2962 is considered to represent the morphological result of such
a detachment of the ameloblast layer.
The impact on the ameloblasts is considered to have caused a
temporary or permanent stop of their secretory activity, and the asso-
ciated formation of hypoplastic enamel defects. In areas, where ame-
loblast secretory activity had eventually been resumed, the initially
formed enamel was prismless (aprismatic), indicating that early after
the restart of matrix secretion the ameloblasts had not yet reestab-
lished their distal Tomes' processes. Corresponding observations have
previously been made in fluorotic cervine and porcine enamel
(Kierdorf et al., 2000,2004; Kierdorf & Kierdorf, 1997).
The extended enamel defect on the paracone of the left M
2
and
some of the smaller enamel defects are diagnosed as posteruptive
lesions. It is suggested that due to a physical impact the enamel in
these locations had flaked off along the grossly accentuated incre-
mental line, which, due to the prism discontinuity, constituted a zone
of reduced mechanical resistance. That an extended loss of enamel
along the accentuated incremental line had occurred only on the buc-
cal side of the paracone of the left M
2
is likely attributable to its prox-
imity to the region of the left M
1
, which had been affected by a
traumatic impact. This impact is considered to have caused damage to
the M
1
and local destruction of the alveolar bone. Alveolar recession
eventually resulted in the loss of the left M
1
. The fact that the (partly
destroyed) M
1
alveolus shows only minor osseous infilling suggests
the tooth was lost relatively shortly before death. We further assume
that the traumatic impact had also caused the posteruptive enamel
FIGURE 3 Left M
2
of the cave bear. (a) Occlusal view of the tooth, mesial (anterior) to top of image. The yellow line indicates the
section plane along which the mesial tooth segment used for microscopic analysis was removed. Arrowhead: cingulum. (b) Polished
section surface of the mesial tooth segment viewed under reflected light, occlusal to top of image. D: dentin, E: enamel, white asterisks: enamel-
dentin-junction (EDJ), black asterisk: area of dentin demineralization, large arrow: fracture plane, small arrow: accentuated incremental line in
enamel. (c) Thin ground section of mesial tooth segment viewed under transmitted polarized light; occlusal to top of image. D: dentin, E: enamel,
asterisks: EDJ, arrow: accentuated incremental line in enamel. Note pronounced Hunter-Schreger banding of the enamel. (d) False-color SEM-BSE
image of polished section surface of mesial tooth segment, occlusal to top of image. The 16 gray-level bands spanning the gray value range from
0 (black) to 255 (peak white) are indicated. D: dentin, E: enamel, asterisk: EDJ, arrows: accentuated line in enamel, arrowheads: accentuated line
in dentin, presenting as zone of interglobular spaces. [Colour figure can be viewed at wileyonlinelibrary.com]
6of10 KIERDORF ET AL.
loss in the left M
2
. Enamel flaking in this tooth is thus considered to
have occurred during life rather than post-mortem.
On macroscopic inspection, the right M
2
, which was not sub-
jected to destructive analysis, also showed enamel defects. These
were diagnosed as pit-type hypoplastic lesions that had partly become
extended by posteruptive loss of enamel. It is suggested that the
hypoplastic lesions extend down to the accentuated incremental line,
which is assumed to exist also in the enamel of this tooth. The brown-
ish staining of the cusp tips of the right M
2
that were affected by
enamel hypoplasia indicates enamel hypomineralization in these
crown areas, suggestive of impaired ameloblast function also
during the maturation stage of amelogenesis. Discoloration of
FIGURE 4 Light microscopic images of thin ground section of the left M
2
of the cave bear, occlusal to top of images. (a) Defect zone in
buccal enamel. The fracture surface of the enamel (arrowhead) is uneven and located slightly internal to the former location of the accentuated
incremental line that is marked by the arrow in the cervically adjacent enamel. D: dentin, E: enamel, asterisk: EDJ. Transmitted light with phase-
contrast enhancement. (b) Defect zone in occlusal enamel. D: dentin, E: enamel, asterisk: EDJ, arrows: accentuated incremental line in enamel,
white arrowhead: exposed accentuated incremental line covered by mineralized deposits (+). Note convexly rounded outline of the defect (black
arrow) and fracture surface of enamel (black arrowhead). Transmitted light with phase-contrast enhancement. (c) Higher magnification showing
“picket-fence”appearance and prism discontinuity along the accentuated incremental line in the enamel (arrows), due to a temporary detachment
of the secretory ameloblasts from the enamel growth front. Note the difference in prismatic structure between the enamel internal to the
accentuated line (iE) and that external to it (eE), asterisk: zone of prismless enamel. Polarized transmitted light. (d) Incremental markings in outer
lateral enamel. Two groups of four laminations (white arrowheads), each group marking three daily enamel growth increments, and the course of
an individual lamination (yellow asterisks) are indicated. Yellow single-headed arrows: prism cross-striations (subdaily markings), yellow double-
headed arrow: width of a daily growth increment, white arrows: course of individual prisms. Polarized transmitted light. [Colour figure can be
viewed at wileyonlinelibrary.com]
KIERDORF ET AL.7of10
hypomineralized enamel has been shown to develop posteruptively
and attributed to infiltration of substances into the porous tissue
(Kierdorf et al., 2004; Kierdorf & Kierdorf, 2007). If the staining
reflected diagenesis of fully mineralized enamel, we would expect also
other crown areas to exhibit enamel discoloration.
A similar sequence of events as that deduced for the cave bear
left M
2
, that is, detachment of the secretory ameloblasts from the
enamel surface followed by the formation of prismless enamel, has
previously been reconstructed for enamel of domestic pigs and wild
boars as a result of excess fluoride exposure during amelogenesis
(Kierdorf et al., 2000,2004; Kierdorf & Kierdorf, 2007). While in some
cases a prismatic structure was eventually reestablished in the
affected teeth, in others the entire enamel formed after the impact
was either prismless or matrix secretion had not restarted at all. In
consequence, hypoplastic enamel defects of different size and depth,
ranging from pit-type to more extended lesions were present in these
teeth. Interestingly, also in some of the fluorotic wild boar teeth, pos-
teruptive flaking-off of larger portions of enamel had occurred along
the grossly accentuated incremental lines (Kierdorf et al., 2000).
In conclusion, a detailed analysis of the enamel defects in the
molars of cranium CER-2962 suggests that they are the result of two
major traumatic impacts. According to our reconstruction, the first
impact occurred during crown formation of the M
2
. This trauma
caused the lesion in the frontal squama and a systemic disturbance of
amelogenesis and dentinogenesis that is manifested by the presence
of accentuated incremental lines in enamel and dentin. The second
traumatic impact affected the left maxilla, leading to the eventual loss
of the left M
1
and intravital enamel flaking along the accentuated
incremental line in the left M
2
. Thus, in the latter tooth, a develop-
mental lesion resulting from a systemic disturbance during crown
growth was later modified (“overprinted”) by a local trauma.
The structure and mechanical properties of ursid enamel have
been studied by several workers (Loch et al., 2022; Renteria
et al., 2021; Stefen, 2001; von Koenigswald, 1992; Weng et al., 2016;
Zikiu & Youheng, 1987). The pronounced Hunter-Schreger banding
observed by us in the analyzed M
2
corroborates earlier SEM findings
by von Koenigswald (1992) on cave bear enamel. In addition, the pre-
sent paper, for the first time, provides information on the nature of
regular incremental markings in ursid enamel. The lines oriented
obliquely to the prism course are laminations, which constitute the
most prominent incremental markings in non-primate mammalian
enamel (Kierdorf et al., 2019; Nacarino-Meneses et al., 2017;
Tafforeau et al., 2007). Labeling experiments in sheep and pigs con-
firmed that laminations constitute daily incremental markings, while
prism cross-striations between consecutive laminations represent
subdaily markings (Emken et al., 2021; Kierdorf et al., 2013). The
enamel secretion rate of 17 to 19 μm/day established for outer lateral
enamel of the cave bear molar corresponds well with values recorded
for the same enamel zone in pig molars (Emken et al., 2023; Kierdorf
et al., 2019). Enamel incremental markings can be used to reconstruct
crown growth and life history parameters of extinct mammals
(Dean, 2006; Funston et al., 2022), and studies using this approach in
cave bear and other ursid species are therefore encouraged.
ACKNOWLEDGEMENTS
The expert technical assistance of Sabrina Kohne and Thomas
Kierdorf is gratefully acknowledged. Two anonymous reviewers pro-
vided helpful comments on the manuscript. Open Access funding
enabled and organized by Projekt DEAL.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflict of interest.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study area available from
the corresponding author upon reasonable request.
ORCID
Uwe Kierdorf https://orcid.org/0000-0003-0531-2460
Dean Konjevi
chttps://orcid.org/0000-0002-8584-9825
Siniˇ
sa Radovi
chttps://orcid.org/0000-0001-7838-7952
Miljenko Bujani
chttps://orcid.org/0009-0000-1421-3339
Horst Kierdorf https://orcid.org/0000-0001-6411-9631
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How to cite this article: Kierdorf, U., Konjevi
c, D., Radovi
c, S.,
Bujani
c, M., & Kierdorf, H. (2024). Analysis of enamel defects
in a cave bear maxillary molar, with remarks on incremental
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