Science - USA (2022-06-03)

and 5 in Bovidae. This might be related to the
dermal nature of giraffoid headgear, with
strong developmental plasticity and flexibility
( 12 ). Ossification centers are not constrained
in specific areas [such as the tip and out sur-
facesinbovids( 18 )] and are distributed deeply

and widely within the headgear ( 14 ). Accord-

ingly, the head-neck morphology of giraffoids

also varies, especially for the elongation and the

thickness of the cervical vertebrae (Fig. 6B

and fig. S17A). These findings raise the pos-

sibility that the variety of giraffoid headgears

as well as the head-neck morphologies were

influenced by different combat styles, as pos-

tulated for the evolution of headgear in female

bovids ( 20 ). For instance, the evolution of thick

cervical vertebrae inD. xiezhiwas related to

head-butting combats, and the evolution of a

Wanget al., Science 376 , eabl8316 (2022) 3 June 2022 4of10

D

Strain energy of atlas (J)

Time (s)

TC model

AC model

AC model with rotation limits

0 0.005 0.010 0.015 0.020 0.025 0.030

3000

2500

2000

1500

1000

500

0

50

40

20

0

-20

0 0.005 0.010 0.015 0.020 0.025 0.030

B

A

TC model

AC model

AC model with rotation limits

C

Rotation of cranium (degrees)

Time (s)

6895

1000

916

833

750

667

583

500

417

333

250

167

83

0

S, Mises

(MPa) A

10270

1000

916

833

750

667

583

500

417

333

250

167

83

0

S, Mises

(MPa) B

8000

6000

4000

2000

0

0 0.005 0.010 0.015 0.020 0.025 0.030

Discokeryx xiezhi

Ovibos moschatus

Ovis ammon

Pseudois nayaur

Strain energy of cranium (J)

E

Time (s)

0 0.005 0.010 0.015 0.020 0.025 0.030

60

50

40

30

20

10

0

Discokeryx xiezhi

Ovibos moschatus

Ovis ammon

Pseudois nayaur

Strain energy of brain (J)

F

Time (s)

Fig. 3. Finite element (FE) modeling for the head-butting behavior inD. xiezhi
gen. et sp. nov. and extant bovids.(A andB) Von Mises stress contour color
maps ofD. xiezhimodels in FE head-butting modeling at a typical time point (0.0048 s),
in comparison between the thick cervical (TC) model (A) and the attenuated
cervical (AC) model (B). In the AC model, the specialized extra articulation
between the braincase and atlas and the intervertebral articulations were removed
from the TC model. (C andD) Dynamic responses ofD. xiezhimodels in FE
head-butting modeling, in comparison between the TC (red) and AC (brown)

models, as well as an AC model with a 5° ventral bending limit of the atlanto-

occipital joint (blue). Note that the ventral overbending of the braincase in the AC

models was revealed by the rotation curves (C) and the large peak values of THCSE

(D). (E andF) Mechanical responses ofD. xiezhicompared with extant head-

butters. Note that in theD. xiezhimodel, the strain energy of the cranium peaked

at the lowest value (E), and the brain vibration amplitude was the smallest among

the four curves (F). Data sources: tables S1 to S3, data S5, code files S1 and S2,

Movies 1 to 3, and movies S4 to S7.

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