How big was the Archbishop?

June 2, 2021

Various Internet rumours have suggested that the Archbishop is a super-giant sauropod one third larger than the mounted Giraffatitan specimen MB.R.2181 (formerly HMN SII). This is incorrect.

Figure E. Skeletal inventory of NHMUK PV R5937, “The Archbishop”, showing which bones were excavated by Migeod’ expedition. Based on a skeletal reconstruction of Giraffatitan brancai kindly provided by Scott Hartman: note that this image does not illustrate the shapes or proportions of the Archbishop material. Bones prepared and available for study are shown in white; those still in jackets awaiting preparation in light grey; those excavated by Migeod but apparently lost or destroyed in dark grey.

Migeod’s assessment of the size of the animal was based on the vertebrae: “The [neck] vertebrae found give a 20-foot [6.10 m] length […] The length of the back including the sacral region was about 15 feet [4.57 m]. The eight or nine caudal vertebrae cover about 6 feet [1.83 m]” (Migeod 1931a:90). This gives the total preserved length of the skeleton as 41 feet (12.50 m). By comparison, Janensch (1950b:102) gives lengths of portions of the mounted skeleton of MB.R.2181 as 8.78m (neck), 3.92m (torso) and 1.07m (sacrum) for a torso-plus-sacrum length of 4.99m. On this basis, the preserved neck of NHMUK PV R5937 is only 69% as long as that of MB.R.2181, but since the first four vertebrae were missing and omitted from Migeod’s measurement, this factor cannot be taken at face value. More informative is the torso-plus-sacrum length, which in NHMUK PV R5937 is 92% the length of MB.R.2181.

This is consonant with measurements of individual elements, which compare as follows:

Table 4. Comparative measurements of Archbishop and Giraffatitan elements

ElementMeasurement (cm)ArchbishopGiraffatitanRatio
Torso plus sacrumtotal length4574990.916
C10 (mC4)centrum length991000.990
C11 (mC3)centrum length104100[1]1.040
D4 (mD3)centrum length27360.750
Longest riblength over curve2352630.894
Left scapulocoracoidlength over curve221238[2]0.929
Right humeruslength1462130.685
Right humeruswidth51590.864
Right iliumlength98123[3]0.797
Right iliumheight7996[4]0.823

Archbishop measurements taken from Migeod (1931a) and converted from imperial; Giraffatitan measurements are for MB.R.2181 except where noted, and are taken from Janensch (1950a:44) and Janensch (1961).
[1] Janensch (1950a) did not report a total centrum length for C11, as its condyle had not been removed from the cotyle of C10; but since the length of its centrum omitting the condyle was, at 87 cm, identical to that of C10, it is reasonable to estimate its total length as also equal to that of C10.
[2] Janensch (1961:181) did not include measurements for the right scapula of MB.R.2181, which is incorporated into the mounted skeleton, but does give the proximodistal length of its right coracoid as 45 cm. Using the 193 cm length given for the similarly sized scapula Sa 9, we can deduce a reasonable total estimate of 238 cm for the scapulocoracoid.
[3] Estimated by Janensch (1950b:99) based on cross-scaling from the fibula and ilium of Find J from the Upper Saurian Marl.
[4] This is the measurement provided by Janensch (1961:199) for the ilium Ma 2, which is incorporated into the mounted skeleton, and which Janensch (1950b:99) considered to match MB.R.2181 very precisely.
[5] Based on a restoration of the midshaft which Janench (1950b:99) calcuated based on other finds.

Individual lines of this table should each be treated with caution: Migeod’s measurements may have been unreliable, and in any case are underspecified: for example, we do not know whether, when he gave a vertebra’s length, he included overhanging prezygapophyses or the condyle. Similarly, we know that Migeod (1931:96) wrote that a rib “was as much as 92.5 inches long”, but we do not know for certain that, like Janensch, he measured the length over the curve rather than the straight-line distance between the ends. And when Migeod says that the ilium “measured 38.5 by 31 inches” we do not know that the height was measured “at the public process”, as Janensch (1961:199) specified.

With those caveats in place, nevertheless, a picture emerges of a sauropod somewhat smaller than MB.R.2181, though by no means negligible. On average, the measurements come out about 15% smaller than those of Giraffatitan.

But this average conceals a great deal of variation. The cervical vertebrae are comparable in length to those of MB.R.2181 (The total of 203 cm for C10 and C11 in the Archbishop, only 1.5% longer than 200 cm for MB.R.2181, is a difference well within the margin of measurement error). The Archbishop’s scapulocoracoid may have been 93% as long as in MB.R.2181. But the limb bones are signficantly shorter (87% for the humerus and a scarcely credible 62% for the femur), and the humeri at least bseem to be have been proportionally more robust in the Archbishop: only 2.86 times as long as wide, whereas the ratio is 3.61 in MB.R.2181. If Migeod’s measurements can be trusted, we have here an animal whose neck is as long as that of Giraffatitan, but whose limbs are noticably shorter. These proportions corroborate the hypothesis that the Archbishop is not a specimen of Giraffatitan.

8 Responses to “How big was the Archbishop?”

  1. […] lepší představu postačí již několik základních údajů, publikovaných nedávno na webu Sauropod Vertebra Picture of the Week. Krk berlínského exempláře (složeného ovšem z fosilií více jedinců) měří na […]

  2. Ronald Says:

    Off topic, but new paper on a new species of giant Australian titanosaur, Australotitan:

  3. Mike Taylor Says:

    Giant sauropods are never off-topic here!

  4. Jem Maybank Says:

    Hey Mike, lovely to meet you this weekend!
    I’ll be lurking on here more to see what I can learn about SVs

    Jem (theropod fan)

  5. Mike Taylor Says:

    Thanks, Jem, welcome aboard!

    If you want to dive into the world of sauropod vertebrae, as everyone should, you might find some of the tutorials helpful:

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