diff --git a/src/schema/meta/templates.yaml b/src/schema/meta/templates.yaml
index 4e7aa668a0..51ff0df059 100644
--- a/src/schema/meta/templates.yaml
+++ b/src/schema/meta/templates.yaml
@@ -153,6 +153,13 @@ deriv:
       segmentation: optional
       scale: optional
 
+  surface_map:
+    $ref:
+      - meta.templates.deriv.surface
+    extensions:
+      - .func.gii
+      - .json
+
 # Entities that apply to most atlas files
 # Include thus:
 #
@@ -164,3 +171,4 @@ atlas:
     entities:
       template: required
       cohort: optional
+      atlas: optional
diff --git a/src/schema/objects/extensions.yaml b/src/schema/objects/extensions.yaml
index 3c7ef248fa..89d97893c9 100644
--- a/src/schema/objects/extensions.yaml
+++ b/src/schema/objects/extensions.yaml
@@ -114,6 +114,22 @@ fif:
   display_name: Functional Imaging File Format
   description: |
     An MEG file format used by Neuromag, Elekta, and MEGIN.
+funcgii:
+  value: .func.gii
+  display_name: GIFTI functional file
+  description: |
+    A GIFTI functional file.
+
+    Per the GIFTI standard: "[A] functional file contains one or more DataArrays
+    with Intent set to NIFTI_INTENT_NONE or one of the statistical intent values.
+    Each DataArray has DataType set to NIFTI_TYPE_FLOAT32.
+    Dimensionality is one with the first dimension set to the number of nodes."
+
+    In practice, this extension is used as a catch-all for scalar data sampled
+    to a surface, with the exceptions of labels (`.label.gii`) and
+    morphometry (`.shape.gii`).
+
+    This extension may only be used in derivative datasets.
 jpg:
   value: .jpg
   display_name: Joint Photographic Experts Group Format
diff --git a/src/schema/objects/suffixes.yaml b/src/schema/objects/suffixes.yaml
index 37cca59edf..05a389ada2 100644
--- a/src/schema/objects/suffixes.yaml
+++ b/src/schema/objects/suffixes.yaml
@@ -727,6 +727,7 @@ meg:
   description: |
     Unprocessed MEG data stored in the native file format of the MEG instrument
     with which the data was collected.
+
 motion:
   value: motion
   display_name: Motion
diff --git a/src/schema/rules/checks/atlas.yaml b/src/schema/rules/checks/atlas.yaml
index 66b127a99b..1540de8604 100644
--- a/src/schema/rules/checks/atlas.yaml
+++ b/src/schema/rules/checks/atlas.yaml
@@ -1,3 +1,4 @@
+---
 AtlasDescriptionRequired:
   issue:
     code: ATLAS_DESCRIPTION_REQUIRED
diff --git a/src/schema/rules/checks/eyetrack.yaml b/src/schema/rules/checks/eyetrack.yaml
index 7f2765b98a..f6133ba02f 100644
--- a/src/schema/rules/checks/eyetrack.yaml
+++ b/src/schema/rules/checks/eyetrack.yaml
@@ -1,3 +1,4 @@
+---
 EyetrackingStimulusPresentation:
   issue:
     code: INCOMPLETE_STIMULUS_PRESENTATION
diff --git a/src/schema/rules/files/deriv/atlas.yaml b/src/schema/rules/files/deriv/atlas.yaml
index 126dad7208..2f835d0ecc 100644
--- a/src/schema/rules/files/deriv/atlas.yaml
+++ b/src/schema/rules/files/deriv/atlas.yaml
@@ -1,3 +1,4 @@
+---
 atlas_description:
   selectors:
     - dataset.dataset_description.DatasetType == 'derivative'
diff --git a/src/schema/rules/files/deriv/imaging.yaml b/src/schema/rules/files/deriv/imaging.yaml
index d4fad4e68c..c44bf14653 100644
--- a/src/schema/rules/files/deriv/imaging.yaml
+++ b/src/schema/rules/files/deriv/imaging.yaml
@@ -396,9 +396,25 @@ pet_pet_volumetric_atlas:
   $ref: rules.files.deriv.imaging.pet_pet_volumetric
   entities:
     $ref:
-      - meta.templates.deriv.volumetric.entities
+      - meta.templates.atlas.base.entities
       - rules.files.deriv.imaging.pet_pet_volumetric.entities
 
+pet_pet_surface:
+  $ref:
+    - meta.templates.deriv.surface_map
+    - rules.files.raw.pet.pet
+  entities:
+    $ref:
+      - meta.templates.deriv.surface_map.entities
+      - rules.files.raw.pet.pet.entities
+
+pet_pet_surface_atlas:
+  $ref: rules.files.deriv.imaging.pet_pet_surface
+  entities:
+    $ref:
+      - meta.templates.atlas.base.entities
+      - rules.files.deriv.imaging.pet_pet_surface.entities
+
 # Masks
 anat_mask:
   $ref: